VTMC 236 Epidemiology Midterm

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EPIDEMIOLOGY WHY: ...knowledge of microbiology and parsitology alone is no longer sufficient to plan, organize and carry out an effective prevention and control of epizootics...

So Study UP!
PUBLIC HEALTH IMPACT: 61% of human diseases (1414)are linked to animals

75% of emerging diseases originate in animals
EPIDEMIOLOGY MEANING: epi - about or upon

demos - populace

logos - science or theory
EPIDEMIOLOGY A COUPLE OF DEFININTIONS: The study of the frequency, distribution and deteriminants of health and disease in populations

Method of reasoning about disease that deals with biological inferences derived from observations of disease phenomena in populations and groups
EPIDEMIOLOGY 8 INVOLVEMENTS: Focuses on poplulations

Involves a very broad definition of disease
- ie health related event

Involves and understanding of the interrelationships between agen, host and environment
- the holy 3 determinants

Involves describing the patterns of disease in relation to individuals, place and time

Involves a logical approach to solving disease problems regarding etiology, predisposing factors, prognoses and appropriate intervention strategies

Involves understanding of change, and and ability to determine whether chance alone can account for observed associations or patterns of disease

Provides and approach for the design, implementation and analysis of observational and experimental research

Involves a systematic approach for the critical evaluation of scientific literature
EPIDEMIOLOGY 3 GENERAL GOALS: Describe the distribution and "size" of disease problems in populations

Evaluate factors affecting the transmission of an organism

Evaluate factors associated with clinically recognizable disease amoung those who are infected
VETERINARY EPIDEMIOLOGY 9 SPECIFIC GOALS: Identify Determinants of Disease
- virtually all clinical disease is multifactiorial

Indentify risks in terms of probability statements
- ie risk is not fixed

Formulate hypothesis about causation
- ie BSE before knowledge of prions

Determine modes of transmission
- tf can fight disease before knowing cause

Develop and evaluate interventions for control and prevention
- ie erradication program

Determine efficacy of new therapeutic and preventive measues
- ie clinical trials

Studying trends over time to make predictions for the future
- ie modeling to develop better responses

Monitoring the animal health of a herd, region or nation
- ie surveillance systems
~~NAHMS, CAHNET

Make the best descision about care of individual patients
EPIDEMIOLOGY 3 INPUTS 3 OUTPUTS: INPUTS
- Who - When - Where
- How - Why
- What to do about it

OUTPUTS
- Descriptive
- Analytic
- Operational
EPIDEMIOLOGY DESCRIPTIVE: Any general observational study of the occurrence of disease of other health related event in a population

Surveys
- main
- representitive sample

Case Reports and Case Studies
- new diseases or new clinical signs of old disease
- not neccesarily epidemiology
EPIDEMIOLOGY ANALYTIC: A hypothesis testing method that investigates the association between a given disease or health releated event and possible causation/factors

Statistics > Association

Association vs Causation
EPIDEMIOLOGY OPERATIONAL 3 ACTIVITIES: An action oriented epidemiology directly aimed at disease control

Control/Eradication/Prevention

Surevillance

Epidemiological Evaluation
EPIDEMIOLOGY THE WORDS BEHIND THE NAME: Ecology
animal Production
socIology
Demographics
mathEmatics
Microbiology
statIstics
parasitOlogy
pathoLogy
ecOnomics
aGriculture
biologY

ok that is pretty sad
KOCH'S POSTULATES 5 AND ASSUMPTIONS 2: The organism must be present in every case of the disease

The organism must not be present in other diseases, or in normal tissues

The organism must be isolated from the tissue(s) in pure culture

The oganism must be capable of inducing the disease under controlled experimental conditions

The organism must then be recovered from the animal and identified

ASSUMPTIONS

A particular disease has only one cause

A particular cause results in one disease
3 SHORTCOMMINGS OF GERM THEORY: Germ theory underestimates the complexity of disease
- multiple etiologic factors
- multiple effects of single causes
- carrier state

Many diseases are not caused by infectious agents
- ie non-agent factors
~~age
~~breed, genetics
MILLS RULES OF INDUCTIVE REASONING WHERE IS THE LOGIC GOOD WHERE IS THE LOGIC BAD: METHOD OF AGREEMENT
If a disease occures under a vairety of circumstances but there is a common factor, this factor may be the cause of the disease

METHOD OF DIFFERENCE
If the circumstances where a disease occurs are similar to those where the disease does not occur, with the exception of one factor, this one factor of its absence may be the cause of the disease

METHOD OF CONCOMITANT VARIATION
If a factor and disease have a dose-response relationship, the factor may be the cause of the disease
- not always true because dose response relationships are not allways linear
~~ a little wine is good, a lot is bad

METHOD OF ANALOGY
If the distribution of the disease is sufficiently similar to that of anothe well understood disease, the disease of cncern may share common causes with the other disease.
- sometimes, sometimes not

METHOD OF RESIDUE
If a factor explains only X% of disease occurrence, other factors must be indentified to explain the remainder, or residue (100-X%)
HILLS CAUSALITY CRITERIA WHAT IS GOOD WHAT IS BAD: STRENGTH
Strong ssociations are more likely to be causal
- but there are weak associations which are causal

CONSISTENCY
the repeated observation of an association in different populations

SPECIFICITY
a cause leads to a single effect, not multiple effects
- complete crap, life was so simple in the '50s and '60s

TEMPORALITY
The cause must procede the effect
- very ZEN, very important to remember!

BIOLOGIC GRADIENT
The presence of a monotonic (unidirectional)dose response curve
- not true for all diseases
~~ remember the wine

PLAUSIBILITY
The biological plausibility of the hypothesis
- can you imagine proposing prions in the '70s
- ok most of you cant imagine the '70s
~~ they were ok it was before the orange of the 80s

COHERENCE
A cause and effect interpretation for an association does not conflict with what is known of the natural history and biology of the disease
- but if you don't know much about it how can you define a conflict

EXPERIMENTAL EVIDENCE
the removal of some harmful exposure in an intervention or prevention program should lead to a drop in the number of cases
- but disease ar e consequences of many factors what if you miss a few through ignorance or logistics

ANALOGY
causal relationship similar to other better known diseases
EVAN'S POSTULATES WHAT DID EVAN INCORPORATE GOOD BAD: Statistics

The proportion (prevalence) of the desease should be significantly higher in individuals exposed to the putative cause than in non-exposed individuals

The exposure should be more common in cases than in those without the disease

The number of new cases (incidence) should be significantly higher in individuals exposed to the putative cause than in non-exposed individuals

Exposure must precede the disease

There should be a spectrum of measurable host responses to the agents (ie antibody response)
- this may be difficuslt
~~ie host response to prions not detectable

The host response should be repeatable following exposure to the putative cause
- can be difficult for some diseases

Elimination of the putative cause should result in a lower incidence of the disease
- but may have other factors producing same disease

Preventing, or modifying, the host's response should decrease of eliminate the expression of disease (vaccination etc)

The disease should be reproducable experimentally
- difficult with many diseases
- may know agents but not mechanisms

The relationship should be biologically and epidemiologically plausable
- biological
~~ the truth is sometimes stranger than fiction
- epidemiologically
~~ may need impractically large sample sizes to show relationships

Note
- Comparison is the basis of epidemiology
- temporality MUST ALWAYS be met but other criteria are often not met
ROTHMAN'S CAUSAL INFERENCE THEORY CAUSE DEFINITION DISEASE DEFINITION: CAUSE

An event, condition or characteristic that PRECEDED the disease event and without which the disease event either would not have occurred at all or at that time

DISEASE

the consequences of multiple causes
ROTHMAN'S CAUSAL INFERENCE THEORY TYPES OF CAUSES - 3 MAIN: Sufficent Cause
- set of minimal conditions and events (COMPONENT CAUSES) that inevitably produce disease
- disease may be produced by different sets of COMPONENT CAUSES
- removal of a particular component cause will prevent a certain amount of disease
- sufficient causes can be hard to determine

Necessary Cause
- one component cause WITHOUT WHICH the dissease cannot occur
- elimination of neccesary cause eliminates all disease
ROTHMAN'S CAUSAL INFERENCE THEORY 4 TYPES OF COMPONENT CAUSES: Predisposing Factors
- increase the level of susceptibility in the hose
~~ age, sex, immune status etc

Enabling Factors
- facilitate manifestation of a disease
~~ housing, nutrition

Precipitating Factors
- associated with the definitive onset of disease
~~ most toxic and infectious agents
~~ breach of immune barriers ie tooth eruption

Reinforcing Factors
- tend to aggravate the presence of the disease
~~ repeated exposure to an infectious agent in absence of an immune response
WEB OF CAUSATION: Representation of all factors thought to relate to presentation of disease
DISEASE DETERMINANTS THE SINFUL SEVEN: Primary Determinants
- neccesary cause

Secondary Determinants
- often component causes

Intrinsic Determinants
- all factors associated with the host

Extrinsic Determinants
- environment and agent

Host Determinants

Agent Determinants

Environmental Determinants
EPIDEMIOLOGIC TRIAD PLUS: AGENT

HOST

ENVIRONMENT

Vector Factors
- relate agent and environment

Husbandry and Management Factors
- relate host and environment
EPIDEMIOLOGIC TRIAD 3 AREAS OF OVERLAP: Host and Agent
- infection
- contamination ie body surface
- pollution

Agent and Environment
- Transmission
~~ related to ability of agent of survive in environment and vectors

Host and Environment
- stress
~~ immunosuppresion
THE AGENT: Biological, chemical, physical, mechanical, social or behavioral entity for which the presence, the excess or dprivation influences the occurence of diesase

A disease could result from the action of a single agent, from several agents each acting separately, or from the interaction of at least two different agents
AGENTS 4 TYPES: INFECTIOUS AGENT

- a living organism that infects a host

NON-INFECTIOUS AGENTS

- Physical
~~ noise, repetitive motin, violence etc

- Chemical
~~ air pollutants, water pollutants etc

- Nutritional
~~ obesity, deficiencies, diet changes etc
INFECTIOUS DISEASE ANOTHER LONG WINDED DEFINITION: An illness due to a specific infectious agent or its toxic products that arises through transmission of that agent or ists products from an infected person, animal or resivoir to a susceptible host, either directly or indirectly through an intermediate plant or animal host, vector or the inanimate environment
TWO OUTCOMES WHEN INFECTIOUS AGENTS STAY IN ANIMAL AND THE UPSHOT: Animal dies and agent is not transmitted

or

Animal kills infectios agent

tf TRANSMISSION is required for the survival of infectious diseases
CHARACTERISTICS OF THE AGENT NAME AND DEFINE 9: Host Range
- the number of species
- variance of environmental conditions
- etc
- the greater the range, the more capable th organism is of spreading and developing disease in animals

Infectivity
- ability of an agent ot establish itself in a host
~~ ie quantity of agent required to create disease

Ability to survive in the Environment
- agents often have part of life cycle outside of host

Pathogenicity
- ability of an agent to produce disease
~~ agents that must live in host to survive cant significantly harm host tf low pathogenicity

Virulence
- measure of severity of disease casued by a specific agent

Antigenicity
- ability of an agent to elicit immune response

Immunogenicity
- ability of an agent to elicit protective immune response in host
~~ ie parasites generally have low immunogenicity

Toxin Production

Resistance Factors

Toxicity
- ability to cause a harmful effect
~~ ie poisons
THE HOST: Organism, usually multicellular, that lodges and maintains in natural conditions a pathogen
THE HOST 4 INTRINSIC FACTORS: Intrinsic host factors do not change relative to disease challenge

Age
- determines immune status of animal
~~ usually lower in young and old

Gender
- diseases releated to male/female physiology, structures, organs, production or reproductive status

Breed
- innate resistance/susceptability
~~local breeds are usually more resistant to disease

Species
- ie foot and mouth in rumminants but not in horses
THE HOST 8 EXTRINSIC FACTORS: Extrinsic host factors are modifiable

Use

Behaviour

Castration/hystorectomy

Movement

Pervious diseases and medications

Feed or Diet

Contacts

Immunization History
THE HOST IMMUNITY: Factors that alter the probability of infection and development of disease in the host after the agent is encountered

Innate Immunity
- barriers that prevent invading pathogens from entering the body
- primarily determined by genetics

Acquired Immunity
- resistance developed by the host as a result of previous exposuer
THE HOST INNATE IMMUNITY: Physical Barriers
- intact skin
- mucosal lining
- repiratory tract cilia
- cough and gag reflex

Chemical Barriers
- acidity of stomach and vagina
- hydrolytic and proetolytic enzymes in saliva and intestines

Cellular and Physiologic Barriers
- macrophages
- NK cells
- inflamation
~~ fever
THE HOST AQUIRED IMMUNITY: The result of a highly specific and evolved response on the part of the host
- begins when the host is exposed to the pathogen

Cellular and Humoral

Immunization
- can modify aquired immunity
- Active
~~ natural or artifical exposure to antigens
- Passive
~~ maternal and therapeutic sources
HOST AGENT INTERACTIONS 4 TYPES: Mutualism
- symbiotic
- beneficial for the host
~~ ie rumen bacteria

Comensalism
- symbiotic
- neutral for the host
~~ ie salmonella in birds

Parasitism
- symbiotic
- detrimental to the host
~~ ie typical disease condition

Phoresis
- host provides transport
~~ ie surface contamination
WHAT DO INFECTION AND INFECTIOUS DISEASE DEPEND ON: Agent and Host Factors

- an agent must be present for an infection to occur
- presence of agent is not sufficient cause for an infectious disease
THE ENVIRONMENT 2 CHEESY DEFINITIONS: Set of natural, social and/or cultural conditions in which organisms live

Everthing that is external to the individual host
THE ENVIRONMENT 8 ABIOTIC FACTORS: Topography

Temperature

Water
- including relative humidity

Soil
- minerals

Pressure

Gases

Air

Climate
THE ENVIRONMENT 2 BIOTIC FACTORS: Flora
- poisons
- nutrition

Fauna
- ie skunks and rabies
THE ENVIRONMENT EPIDEMIC INFECTIOUS DISEASES SEASONAL CONSIDERATIONS OF 4 TRANSMISSION MECHANISMS: Direct Physical Contact
- low seasonal affects because infectious agent in environment for very short time
- sporatic spread
- closed commmunities
- involves whole herd

Airborne Droplets
- travel better when humidity higher
- rapid spread
- universal
- often involves young

Arthropod Borne Outbreaks
- more prevalent in summer
- gradual build up (amplification)
- follow population dynamic of vectors
- may combine biological and mechanical transmission

Vehicular
- summer and fall afford better conditions for agent survival
- explosive outbreaks
- follows economic distribution routes
- common source
~~ ie water or feed
THE ENVIRONMENT SOCIOECONOMIC 3 ELEMENTS: Cultural Background
- ie old Spanish farmers like to swap rams

Political
- laws
- policies
- almost allways involved in disease

Economic
- prices
- subsidies
~~ ie motivated to keep older more susceptable sheep
THE ENVIRONMENT ANIMAL MANAGEMENT 7 FACTORS: Farm characteristics

Housing
- ventilation
- sanitation

Husbandry

Animal Stocking Density
- especially respiratory transmission

Animal Movement

Environmental Conditions
- temperature
- humidity

Nutrition
- protein
- energy
THE ENVIRONMENT ANIMAL MANAGEMENT A COUPLE OF SAGE SAYINGS: Every care or lack of care effects disease in animals

Bovine mastitis is a disease of man with signs in the cow
PATHOGENS 4 SOURCES: Living Organisms

Carcasses

Animal Products

Environment
SUSCEPTIBILITY: Susceptability is what makes and animal infected

or

The state of being readily infected by a pathgen
- ie the infectivity

Relative to a given agent hosts are
- susceptable
- non-susceptable
SUSCEPTABLE ANIMALS: May or may not express disease after infection

- agent factors
~~ pathogenicity

- individual factors
~~ age, sex etc

- species factors
~~ a given agent will manifest disease in some species but not others
GRADIENT OF INFECTION AND DISEASE STATUS TYPE SPECTRUM: Status of Animal
Type of Infection
Spectrum of Disease

Non-Susceptable (immune)
- no infection
~~ no signs

Susceptable

- unapparent infection
~~ no signs
-~- no disease
-~- subclinical disease

- overt infection
~~ clinical signs
-~- mild
-~- severe
~~ death
INCUBATION PERIOD: From infection to the development of the clinical manifestations of disease
PREPATENT PERIOD: aka Latent

Interval between infection and the fist shedding of the pathogen
INFECTIOUS PERIOD: Duration of infectiousness of animal
PREVENTION 3 TYPES AND DEFINITIONS: Primary Prevention
- activites aimed a halting the occurrence of a disease before it happens
~~ immunization
~~ decontaminations
~~ personel hygiene
~~ eliminationn of reservoirs
- occurs in prepatent (latent) period

Secondary Prevention
- activities directed at detecting carriers of infection
~~ find the asymptomatic
- occurs before clinical disease

Tertiary Prevention
- treatment of affected individuals in order to halt the progression of the disease
~~ limit disability
~~ rehabilitation
- occurs after clinical disease
SIX SUSCEPTIBLE ANIMALS: UNAPPARENT INFECTION

Healthy Infected Animal
- salmonella in chickens
- doesn't create disease

Incubating Animals
- BSE in cattle
- very long incubation period
- tf infected but not showing disease

Recovered/Convalescent Animals
- sterilizing immunity ie completely clear virus
- harbour pathogen ie do not completely clear virus
~~ continuously or periodically shed

Chronic Latent/Persistent Infection
- infected in utero tf recognize virus as self
- continually shed
- eventually develop disease

Intermittent Shedders
- ie cows sheding E coli 157 when diet suddenly changed
FMD ROLE OF 3 LITTLE HOSTS: Pigs
- amplifiers
- shed very high levels of virus

Cattle
- indicators
- show clinical signs withing one day

Sheep
- maintenance hosts
- late onset of clinical signs
- tf undetected
HOSTS 9 TYPES: Note Definitions are not mutually exclusive

Reservoir
- infectious agent normally lives and multiplies
- tf common source of infection to other animals
- almost all hosts can act as resevoirs

Definitive aka Final
- organism undergoes its sexual phase of reproduction
~~ ie parasites
- or ends its dynamic process

Primary aka Natural aka Maintenance
- maintains an infection in an endemic area
- host unaffected
~~ ie ASH in wild boars
- host unaffected

Secondary
- species involved in the life-cycle of an agent outside typical endemic areas
- ASH outbreaks in European pigs

Paratenic
- transport infectious stages of a parasite to the definitive host
- no development of the parasite occurs
- can be mechanical vectors

Intermediate
- infectious agen undergoes some development
~~ often asexual reproduction

Incidental aka Dead End
- develop disease but not involved in transmission
- infection dies in host
- ie WNV in humans and horses

Amplifier
- produces large quantities or transmission of virus
- ie birds with WNV infect 100s of mosquitoes

Hibernating
- parasite hibernates with host
INFECTED ANIMAL PRODUCTS 8 TYPES: Amount in products is usually low
- ie subclinical
- treatment may amplify pathogen

Milk and Milk Products
- brucellosis

Eggs
- salmonellosis

Bone, Meat and Bone Meal
- BSE

Serum
- bluetongue virus in canine vaccines

Tissue
- ovine pestivirus in Aujeszky vaccine

Exceta
- salmonellosis
- avian flu

Semen and Embryos
- campylobacteriosis
- BVDV
TRANSMISSIBLE DISEASES OBLIGATORY 2 BIT DEFINITION 2 TYPES: Diseases whose agents can be transferred from one individual host to another

CONTAGIOUS
- those requiring contact (direct or indirect)with the individual that is the source of the pathogen
- ie rabies, FMD

NON-CONTAGIOUS
- transmitted through the intermediary of a vector or vehicle
- ASH, BSE
MODES OF TRANSMISSION: Vetrical Transmission
- infection is passed on to the progeny

Horizontal Transmission
- between animals that are not necessarily related
- contact
- vehicle
- vector
VERTICAL TRANSMISSION 2 WAYS TO PLAY: Hereditary
- agent transmitted within the genome
~~ retroviruses ie HIV

Congenital
- prestented at birth
- in utero or in ovo
- Germinative Transmission
~~ chicken leucosis viruses
-~- infects superficial tissues of ovary
- Transplancental Transmission
~~ during gestation
~~ abortions
~~ still births
~~ infected offspring
~~ permanently infected offspring
- At Parturition
~~ herpesvirus
HORIZONTAL TRANSMISSION CONTACT 2 WAYS TO PLAY: DIRECT CONTACT
- requires physical contact
- fragile agents
- cutaneous or mucosal contact
- venereal transmission
- bites

INDIRECT CONTACT
- urine
- feces
- salivary
- droplets from sneezes, coughs
- milk
HORIZONTAL TRANSMISSION VEHICLE: Fomites
- Mechanical
~~ physical tranfer agent
~~water, air, equipment

- Biological
~~ supporting multiplication and/or development
~~ milk
FOMITE: An object or material thai is not in itself harmful, but on which pathogens may be conveyed
- clothing, equipment etc
- transmission always depends on ability of agent to survive on fomite
- equine strangles
HORIZONTAL TRANSMISSION VECTOR 2 TYPES: MECHANICAL aks Passive
- pathogen does not replicate
- life of agent on vector is limited

BIOLOGICAL

- Propagaitve Transmission
~~ must exceed blood threshold
~~ may replicate
~~ no morphological changes
~~ no intermediate hosts
~~ ticks act as vector and reservior
~~ other insects act as vector only

- Ciciopropagative (Developmental) Transmission
~~ agent must remain in agent for extrinsic incubation period
~~ may or may not replicate
~~ developmental changes
~~ intermediate host
BLOOD THRESHOLD: [] of agent required in blood of host in order to infect vector at a level required to infect another host
EXTRINSIC INCUBATION PERIOD: Time between infection of vector and viability of agent to be capable of infecting new host
- agent requires developmental time in vector
PORTAL OF ENTRY: The routes by which an infectious agent can infect a susceptible animal
PORTAL OF EXIT: The routes by which an infectious agent exits its host
- feces
- urine
- saliva
- expired air
- blood
- semen
- urogenital secretions
PORTALS OF ENTRY AND EXIT 13 WAYS MAMMALS CAN LEAK: Conjunctiva

CNS

Circulatory System

Skin

Urinary System

Anus
- preg checking can you say iatrogenic

Fetus

Genital System

Mammary Gland

Alimentary System

Respiratory System

Oral Cavity

Nasal Cavity
FMD ROUTES OF INFECTION: Cattle
- more susceptible to infection by the repiratory route

Pigs
- more susceptible to infection by the oral route
FMD DURATION OF VIRUS EXCRETION CATTLE: 11 Days
- Saliva

10 Days
- semen

7 Days
- urine
- nasal discharge

5 Days
- blood
- milk
- aerosol
- feces
AGENT MAINTENANCE STRATEGIES 5 HANDY ONES FOR THE MIDTERM: Avoidance of stage in external environment
- vertical transmssion
- arthropod borne
- direct contact

Development of resistance forms
- ie sporulation in anthrax
~~ good for 40 yrs
~~ evil fields

Rapid In - Rapid Out
- short life in host and environment
- tf rapid
~~ infection
~~ multiplication
~~ escape
- respiratory diseases
- works best in high density conditions

Persistence within the host
- adapts to host defence mechanisms
- long incubation

Extension of Host Range
- zoonoses our favorite
SPREAD OF INFECTION MENAGE a TROIS: Host
- Susceptability
- apparent disease
- infectiousness

Pathogen
- infectivity
- stability (resistance)

Effective Contact
- routes of infection
HERD LEVEL MODES OF TRANSMISSION: Infection from neighboring farms
- vectors
- contact

Infection by Introduction
- animals
- objects
- people

Infection due to resurgence of the disease
- anthrax
- intermittent shedders
HERD LEVEL SPREAD OF INFECTION: Transmissibility
- agent strategy of maintenance

Extent to which animals in the herd are receptive to infection
- proportion of susceptible and resistant animals

Animal Husbandry
- stocking density
- loose vs tethered housing
- movement within herd
HABITAT AND TRANSMISSION WHERE WHO HOW: WHERE
- Sources of Infection
~~ measures aimed at destroying the pathogen in situ

WHO
- Susceptibility of Host
~~ measures aimed at reducing susceptibiliy to infection

HOW
- Modes of Transmission
~~ measures aimed at preventing transmission
DISEASE CONTROL MEASURES 2 MAIN DIVISIONS: Sanitary Measures
- Primary Prevention
- eliminate agent from environment
- tf avoid infection or exposure of health individuals

Medical Measures
- only acts on hosts
- direct protection of healthy animals
- treatment of sick animals
SANITARY MEASURES 3 SOUND BITES: Detection of the Disease

Offensive measures on infected farms to remove disease
- contain disease
- control outbreak
remove the disease

Defensive measures on disease free farms to protect them from disease
DETECTION OF DISEASE: Systematic Screening
- active detection
- non clincal
~~ looking for disease in apparently healthy animals
- clinical
- antibody or agent detection
- laboratory

No Screening
- passive detection
- mainly based on signs or lesions
- farmers, vets, abattoir
OFFENSIVE MEASURES REMOVING DISEASE: Measures to CONTAIN MOVEMENT of disease
- animals
- tissues
- fluids

Isolation

Trace Back and Action
- determine when herd infected
~~ incubation period
~~ pepatent period
~~ infectious period
- animal with oldest lesions is usually the index case

Follow up and action
- materials and animals that have moved since begining of incubation period
OFFENSIVE MEASURES CONTROL OUTBREAK: Slaughter

Environmental Sanitation

Individual Treatment and Isolation
SLAUGHTER INDICATIONS 5 CRITERION: Spontaneous Development of Infection
- slaughter when permenant infection
- ie chronic wasting disease

Treatement Availability
- slaughter when treatment not available or economically prohibitive
- ie paratuberculosis

Potential for Spread
- slaughter if risk is high
- ie FMD or AI

Zoonotic Status
- slaughter if major zoonosis
- ie brucellosis

Epidemiological Status
- Exotic or Rare disease
- AHS, ASF

Epidemiological Mechanism
- slaughter if absence of enviornmental or wildlife resevoir
- Aujeszky's disease
TOTAL AND IMMEDIATE SLAUGHTER 4 REASONS THAT WORKED FOR MALOSAVICH: aka Depopulation

- highly contagious diseases

- no tests to allow selective slaughter

- population inaccessible to perform other measures

- no other method of control available
PARTIAL AND PROGRESSIVE SLAUGHTER: aka Selective

Disease not highly contageous

Indentify infected individuals
- reqular testing
- remove as soon as possible
DEFERRED SLAUGHTER: Form of selective slaughter

Slow spreading diseases

keep animal as long as productive
- ie through pregnancy
ENVIRONMENTAL SANITATION 3 ELEMENTS: Disinfection
- destruction of disease agent in environment
- limited by
~~ extremely resistant pathogens
~~ latent carrier status
-~- sheds after disinfection event
~~ intermedisate host
-~- reintroduces agent
- steps
~~ cleansing
~~ disinfection
~~ dry out period before restocking
~~ second disinfection

Vector Control
- vector borne diseases

Rodent Control
- intermediate or paratenic hosts
CERTIFICATION OF DISEASE REMOVAL: Total Slaughter

Partial Slaughter
- requires 2 consecutive negative tests
RESTOCKING 3 STEPS TO STOCKING: Initially introduce small number of animals

Check health status after incubation period has elapsed

Introduce remaining stock
DEFENSIVE MEASURES 2 GOALS: aka BIOSECURITY

Reduce or prevent
- introduction of new diseases
- movement of infectious diseases
BIOSECURITY 7 SOURCES OF INFECTION: Wind

Water

Animals
- purchase
- quirantine
- screening

Humans
- boots
- clothing

Vehicles and Equipment

Animal Products

Neighborhood
- contact with any of above
BIOSECURITY PROGRAM 4 DESIGN COMPONENTS: Risk Assessment
- level of infectious diseases already present

Identification of Priorities
- which diseases are important

Assessment of Diseases NOT Present

Development of Plan
SANITARY MEASURES 4 LIMITATIONS: Wildlife Reserviors

Soil Reseervoirs

Endemic Highly Contageous Diseases

Phychological Obstacles
- established farms reluctant to cull or make changes
SANITARY MEASURES ADVANTAGES DISADVANTAGES: Advantages
- no vaccines required
~~ avoid cost, stress etc
- avoid cross reaction of vaccine with tests
~~ allows culling program

Disadvantages
- must be done on ongoing permanent basis
~~ cost
- constant risk of infection
MEDICAL MEASURES: Treatment
- reduce shedding period
- antibiotics
- chemo-prophylaxis

Immunization
- timing must be appropriate
- active
~~ vaccines
- passive
~~ sera
VACCINE EFFICACY 5 CONSIDERATIONS: Vaccine Characteristics
- live
- innactivated

Proportion of immune competent animals

Proportion of animals that actually get vaccinated

Vaccine Management
- storage specifications
~~ ie how long did it spend on your dashboard in july
- label usage

Environmental Factors
- status of the disease
- epidemiology of the disease
VACCINE EFFICACY TAO OF: Grasshopper:

Rain is Disease

Umbrella is Vaccine
HERD IMMUNITY EVENING NEWS SOUND BITE: The indirect protection from infection of susceptible animals of a population and the protection of the population as a whole, which is brought about by the presence of immune individuals

Because disease spreads from animal to animal, the probability of reaching a susceptible animal decreases as the proportion of immune individuals increases
HERD IMMUNITY POPULATION COMPOSITION THE 10 COMPONENTS: Compostition of Herd Population
- incubating
- infected
- sick
- convalescent
- shedding
- vaccinated
- recovered
- susceptible
- alternative hosts
- alternative carrier animals

Note also have to consider
Contact Rate
- interaction among animals
~~ behavior
~~ husbandry
HERD IMMUNITY BASIC REPRODUCTION RATE DEFINITION 3 FACTORS FORMULA 3 VALUES: The average number of secondary cases directly infected by an infectious individual dureing its ENTIRE infectious period, when it enters a TOTALLY susceptible population

B = risk of transmission per contact
- aka probability of transmission or attack rate
K = number of contacts per unit of time
D = duration of infectivity
- infectiousness

Ro = B x K x D

Ro > 1 = Epidemic
Ro = 1 = Endemic
Ro < 1 = Eradication
HERD IMMUNITY HOW MUCH IS ENOUGH: Require that

p > 1 - 1/Ro

Where

p = proportion of immune population
Ro = basic reproduction rate

Average diseases have Ro of about 7 tf a herd immunity of about 85% will do
HERD IMMUNITY 4 REQUIREMENTS: The disease agent must be restricted to a single host species

Transmission must be relatively direct from one member to another

There must be NO outside reservoir
- provides alternate means of transmission

Infections must induce solid immunity
PREVENTION WHAT IS IT: Application of measures designed to exclude disease from unaffected populations

First line of defence against a disease
PREVENTION STRATEGIES FOR PRESENCE AND ABSENCE OF DISEASE: Absence
- quarantine

Presence
- mass immunization
- chemoprophylaxis
- environmental control and hygiene
CONTROL WHAT IS IT: Reduction of the prevalence of a disease to a level where it is no longer considered a major health and/or economic problem
~~ ie acceptable losses to producers
CONTROL 4 STRATIGIES: Preventing the spread of disease

Decreasing communicability

Increasing resistance

Early detection and diagnosis
WHY ERADICATE: Complete elimination of the agent from a specific region usually has greater econimic benefits than controlling agent
ERADICATION 5 CRITERIA FOR SUCCESS: Profitable

Method of Diagnosis

Isolation of the Agent

Removal of Sources of Infection

Protection of Susceptible Animals
CONTROL STRATEGIES 3 FRACTIOUS FACTORS: Nature of Disease

People

Infrastructure
6 IMPACTS OF NATURE OF DISEASE ON CONTROL STRATEGIES: Cause
- one necessary cause
- or multifactorial disease

Host Range and Survival in Environment
- wildlife reserviors
- intermediate hosts

Host Agent Interaction
- clinical signs
- effective antibody responses

Transmission
- Vertical
- Horizontal
- Direct
- Indirect

Diagnostic Methods
- fast
- inexpensive
- accurate

Treatment and Intervention
- therapeutic measures
- preventitive treatment
3 IMPACTS OF PEOPLE ON CONTROL STRATEGIES: Economic Considerations
- cost effectiveness of program

Political Issues
- production limiting diseases
- public heath concern
- precautionary principle
~~ if don't know much about the disease and public concern is high must be seen to do something
-~- ie cull civet cats for sars, only one of many reservoirs

Cultrual and Social Factors
- culling cattle in Inida
- killing wildlife in Britan
6 IMPACTS OF INFRASTRUCTURE ON CONTROL STRATEGIES: Participants
- veterinary authorities
- laboratories
- livestock industry

Veterinary Infrastructure
- mobile field service
- diagnostic facilities
- research facilities

Diagnostice Capability
- rapid recognition of disease

Adequate Surveillance

Availability of Replacement Stock

Suitable Legislation
- enforcement
- compensation
INDIVIDUAL HERD CONTROL 6 CRITERIA FOR IMPLEMENTATION: Spread of agent is stopped by physical barrier
- ie fence

Rate of spread is slow enough to permit intervention before entire herd becomes infected

Carriers of the disease can be detected on the farm

Agent does not harm people

Agent causes low to high morbidity with low or no mortality

Highly effective vaccine or treatment is available
REGIONAL CONTROL 6 CRITERIA FOR PUSHING THE BIG RED BUTTON OR WHEN NOT TO SHOOT, SHOVEL AND SHUTUP: Agent readily passes physical barriers

Rate of spread is to fast to permit intervention before the entire herd becomes infected

Apparently healthy carriers sisseminate the disease that can be detected only by laboratory tests

Agent is a human pathogen

Agent causes high morbidity and high mortality

Vaccine or treatment is only poorly to moderately effective
PREVENTION, CONTROL AND ERADICATION 8 GENERAL STRATEGIES: Vaccination
- protect against infection and or disease

Removal of reactors combined with vaccination of susceptible animals
- high prevalence of moderate contagious diseases
- segragation of herds inadequate

Removal of reactors only
- non highly contagious diseases
- long incubation period

Herd depopulation
- highly contagious diseases
- difficult to diagnose diseases
- short incubation period

Surveillance with/without Vaccination
- diseased animals will die or recover without being carriers

Barriers or isolation
- swine, poultry industries

Elimination of carriers or vectors

Educational activities
- whys and hows
MOSS: disease MOnitoring and Surveillance Systems
- pathetic

Systems for collection, analysis and dissemination of information on animal health related events
DISEASE MONITORING: Ongoing efforts directed at assessing the health and disease status of a given population

focuses on identifying a diseas or group of disease to ascertain changes in prevalence and to determine the rate and direction of disease spread

Lacks action to prevent or contral a helath problem
DISEASE SURVEILLANCE: Directed at a specific disease

Includes an action to prevent or control the health problem thaat is being monitored

Requires
- a defined monitoring system
- a defined threshold for disease level
- predefined directed actions and interventions
WHY HAVE A MOSS 3 PERSPECTIVES: To minimize the negative effects of health related events in the animal population that affect

Animal health and Welfare
- knowledge of the extent of endemic diseases
- required as part of any control/eradication program

Public Health
- eradication of major zoonotic diseases
- required as part of any eradication program

Trade in animals and animal products
- evidence about the absence of dieseases
- extent of endemic diseases
- early warning systems for FADs (foriegn animal diseases)
- minimize political interference
~~ can you say RCALF?
MOSS 3 MAIN OBJECTIVES: Monitoring and Surveillance of endemic animal diseases and infections

Monitoring and surveilliance of FADs

Monitoring of risk factors
MOSS ON FADS: Early warining of exotic (aka new) diseases

Spatial-Temporal Distribution of Diseases

Detection and surveillance of other countries diseases
- if status in other countries is known can take steps to prevent entry

Prove the absence of diseases
RAUL'S FAVORITE FAILURE OF A MOSS: FMD in Britian
USING A MOSS TO PROVE ABSENCE OF DISEASE 8 STEPS TO ABSTAINENCE: Intent to eradicate

No clinical disease

Provisional freedom from disease

Stop vaccination

No clinical disease and no vaccination

Observe freedom from disease

Serological surveillance

Establish freedom from disease
MOSS MONITORING AND CONTROL OF RISK FACTORS: Track factors associated with endemic diseases
- ie trends in numbers of vaccine doses administerd

Control of factors associated with the introduction of new diseases
- ie importation regulations
4 REASONS TO CONSIDER A DISEASE FOR MOSS: Zoonotic
- public health role

Highly Contagious

Severe economic impact

Trade impact
DISEASES OF INTEREST IN CANADA 3 CATEGORIES: Reportable Diseases
- significant importance to
~~ human or animal health
~~ Canadian economy
- report every case or SUSPICION of a case
- vets report

Immediately Notifiable Diseases
- diseases exotic to Canada for which there are no control or eradication programs
- laboratories report

Annually Notifiable Diseases
- diseases for which Canada must submit an annual report to the OIE indicating their presence within Canada
MOSS INFRASTRUCTURE 6 ELEMENTS: Vetrinary Services

Laboratories

Livestock Industries

Communication

Economic Resources

Legal Basis
- ie Animal Health Act
DESIGNING A MOSS 11 CONSIDERATIONS: Definition of Objectives

Indentification of indicators of health event
- # of cases
- incidence and prevalence
- production indicators

Development of case definitions
- serology
- symptoms
- postmortem lesions etc

Indentification of data sources
- laboratories or practioners

Sampling design
- unit of analysis
- target population
- sampling strategy

Amount and frequency of data collection
- continous
- interval

Method of data collection
- active
- passive
- sentinel herds

Validation of the system

Analysis of survellance data

Development of dissemination methods

Evaluation of survellance systems
- Sensitivity/Specificity
- timeliness
MOSS PASSIVE COLLECTION: No specific effort to collect data
- tf submitted to central units under obligation
- ie reportable diseases
MOSS 7 YESES TO SUCCESS: Animal shows clinical signs

Suspected clinical case identified by owner

Suspected clinical case reported to or indentified by vet

clinical suspicion confirmed by vet based on expertise

decision by vet to submit biological samples

appropriate samples of sufficient quality submitted
- can you say anatomy and dashboard?

Correct diagnostic procedure performed
MOSS PASSIVE COLLECTION 5 ADVANTAGES: Indentification of diseases

Detect outbreaks

Response to outbreaks

Inexpensive

Minimum requirement
- OIE
MOSS PASSIVE COLLECTION 8 DISADVANTAGES: Need of clinical signs
- long incubations signs

Incidence or prevalence

Representativeness

Geographical distribution

Free of disease
- not a guarantee

Priorities

Less motivation
- involved people may be unaware of obligations

Influenced by awareness and level of knowledge
MOSS ACTIVE COLLECTION 7 ADVANTAGES: Not restricted to clinical cases

Proper amount of information

Representativeness

Estimates of incidence or prevalence

Rapid

Profitable

High Motivation

Note active involvement of veterinary health authorities
MOSS PASSIVE COLLECTION 2 DISADVANTAGES: Costly

Requires high level of organization
SENTINEL NETWORKS WHAT ARE THEY ADVANTAGES DISADVANTAGES: Type of active collection
- based on sentinels
~~ ie big white swans for AI
- based on hot spots
~~ ie markets

ADVANTAGES
- identify outbreaks
- changes in prevalence/incidence
- evaluation of disease control programs
- cost effectiveness
~~ not testing whole country

DISADVANTAGES
- not population based
~~ tf may not be representative
- may be ineffective without prior knowledge of disease distribution
MOSS DATA ANALYSIS AND INTERPRETATION: Estimate
- incidence
- prevelence

Identify Risk Factors
- OR
- RR

Impact
- AR
- AF

Identify temporal and spatial clusters
MOSS USE OF RESULTS: Evaluation and/or implementation of programs and stregies
- disease frequency
- risk factors
- program profitability
- ability to eradicate

Establish freedom from disease

Research Projects
- secondary source of data
AVIAN INFLUENZA 10 DEFINING FACTOIDS: Not emerging disease
- very old

Infecitous disease of birds

All AI is caused by type A strains of influenza
- orthomyxovirus
- all A subtypes found in birds
- humans have B and C strains

Worldwide occurrence

Present in > 90 species of birds representing 12 orders

Wild birds are usually asymptomatic

Clinical signs in poultry range from mild to severe

Issue for international trade in poultry and poultry products

Costs associated with control in poultry can be high

Is really an emerging sense of emergency
INFLUENZA FACTIODS: AI is a Zoonotic AI
- H5, H7 and H9 strains transmit from bird to humans
- pathogenicity varies from conjunctivitis to rapid pneumonia

Seasonal Influenza
- contagious respiratory illness
- caused by human influenza viruses
~~ H1 - H3

Epidemic Inflenza
- large outbreak of illness that spresds easily from person to person
~~ H1 - H3

Pandemic Influenza
- global outbreak of illness that spreads easily from person to person (H1 - H3)
AI VIRUS FACTIODS: RNA Virus

8 gene segments

10 proteins
- H (Hemoglutinin) for docking
- N Neurimididase for release of virus

16 H types

9 N types

Matrix proteins are used to identify subtypes

Polymerase is sloppy
- tf high mutation rate via antigenic SHIFT

Can mutate to high pathogenicity
- especially in intensive poultry operations
- note pathogenicity is defined by experimentally infecting chickens not people (we wish) or wild birds
INFLUENZA AGENT AND ENVIRONMENT: Weak Virus

Heat inactivated

Preseved by cold
- tf seasonal in wild populations

Cyclical pattern with peaks in cooler months in humans
- behavior related

Primarily water borne in wild bird cycle
- shed in feces

Strong seasonal patterns in wild birds
- viral surviablility
- host behavior
TYPE A INFLUENZA HOSTS: Wild Birds
- waterfowl
- shore birds

Domestic Poultry

Swine

Horses
- existing vaccines

Humans

Other Mammals
- mink
- whales
- seals
- dogs
~~ low pathogenicity
~~ probably jumped from horses
AI HOST TRIAD ECOLOGY: Wild Birds
- reservoir for all subtypes
- spillover to domestic birds
- allways fecal/oral transmission

Domestic Birds
- Amplifiers
~~ viral numbers
~~ viral mutations
- initial tranmission fecal/oral
- Backyard Flocks
~~ high risk of exposure
~~ high resistance
~~ low amplification
- Commercial Flocks
~~ low risk of exposure
~~ low resistance
~~ high amplification
~~ respiratory transmission
- Spillback to wild birds
- Zoonotic

Humans
- transmission usually via exposure to dead birds
- possible spillback to domestic birds
HOSTS MIXING VESSELS: Pigs
- high stocking densisty drives antigenic shift
- receptors for both human an avian viruses
- tf potential to combine strains

Humans
- also act as mixing vessels
- tf normal influenza plus H5N1 > pandemic
AI INCUBATION CLINICAL SIGNS LP AND HP: Incubation Period
- 3 to 5 days

Low Path
- slow onset
- often undetected
- ruffeled feathers
- mild respiratory signs
- mild reproductive signs
- drop in egg production
- low mortality rates
~~ ie rise from 5% to 8%

High Path
- sudden onset
- death within 24 to 48 hours
- severe systemic disease
~~ colonizes entire body ala ebola
- respiratory signs
- neuological signs
- high mortality
~~ 90 to 100%
AI SHEDDING 3 WAYS IN DOMESTICS: Feces

Nasal Secretions

Saliva
AI TRANSISSION COMMERCIAL POULTRY SEVEN WAYS TO MAKE THE EVENING NEWS: Movement of infected birds

Contaminated feed and water

Contaminated equipment

Egg Flats

Feed Trucks

Personel

Aerosol
- up to 5 kms
- barn to barn if commercial
HISTORY OF HPAI OUTBREAKS POULTRY: 24 epizoontics of HPAI since 1959

All H5 or H7 subtypes

No concurrent humman infection until 1997

A/chicken/Canada/AVFV/04 H7N3
- Fraser Valley BC
- 42 commercial
- 11 backyard flocks
~~ including pets
- 16 million chickens depopulated
- 2 humans develop conjunctivitis
- $360 M direct losses
- $150 M downstream losses
HISTORY OF AI IN HUMANS: 8 zoonotic outbreaks since 1959
- not including H5N1
- all H5, H7 or H9
- LP and HP

Usually isolated cases of mild disease except
- 1997 18 humans in Hong Kong
~~ associated with H5N1
~~ 6 human fatalities
- 2003 88 humans in Holland
~~ associated with H7N7
~~ conjunctivitis
-~- 1 death but it was only a vet
- 2003 H5N1 re-emerges in SE Asia
HISTORICAL PANDEMICS: Usually 3 - 4 per century

1918 Spanish Flu
- AI found way into people
- H1N1
~~ reconstructed from human remains
- 20 to 40 die
- uniquely pathogenic
~~ tf no human immunity
- immunosupression via rationing?
- transmission via troop movement
- disproportionate mortality
~~ 15 to 45 yo

1957
- H2N2
- contained 3 genes from AI

1968
- H3N2
- H2 disappears
~~ this is common with influenza viruses
H5N1 OUTBREAKS TEMPERO-SPATIAL: Jan 04 to Jun 05
- Mainly SE Asia

Jul - Dec 05
- moved west to Europe
- transasian railway
~~ bird migration is mainly north-south

Jan 06
- Most of Europe
- Africa via smuggling from Turkey

H5 in 50 Countries

H5N1
- confirmed 39 countries
- lag due to requirement to culture virus to determine N type
H5N1 TOP 3 COUNTRIES WHY: Veitnam

Thailand

Indonesia

Socioeconomic
- people live with poultry
- high human cases
~~ culling
QUINHAI LAKE: aka STU

Ground Zero
- April June 2005 China
- 6345 mortalities
- initially spread by fall migration

Only second H5N1 panzootic recognized in WILD birds
TELL ME SOMETHING UNUSUAL ABOUT H5N1: Gets into mammals

- cats
~~ free range
~~ captive
~~ experimental

Pigs

Macaques

Rats, Rabbits, Ferrets

Stone Martens
H5N1 AND HUMANS A FEW FACTIOIDS: 101 deaths of 180 KNOWN cases since 2003
- 60% mortality or undiagnosed cases?

East Asia and the Pacific
- Cambodia
- China
- Indonesia
- Thailand
- Vietnam

Europe and Eurasia
- Turkey
- Azerbajian

Family Clusters
- common risk factors
- or human to human transmission

Major risk factor is contact with live or dead infected poultry
- raw poultry products may also pose risk
H5N1 OLD WORLD EPIDEMIOLOGY: Detection
- thresholds
- sentinels

Pattern matching
- time
- space

Role of Different Hosts
- carriers
- amplifiers
- bridges
- accidnental victims
~~ mammals and humans are dead end hosts

Genetics and Phlogenics
- Quinhai lake strain widely spread

Tipping Points
- HK 1997
- Quinhai 2005
H5N1 IS IT ENDEMIC: Yes
- has been in China for 10 years
MUTE SWANS WHY DO WE LOVE EM: The are
- Big
- White
- tf highly visble
- die from H5N1

tf they make great SENTINALS
AI MANAGEMENT 3 LEVELS: Socioeconomic not Scientific

Prevention
- NA has a shot at this

Control
- Perhaps in Urasia

Eradication
- not a chance
- endemic in China
AI MANAGEMENT 6 TOOLS: Survelliance

Prevent exposure
~~ biosecurity
~~ trade restrictions
~~ quarantine

Vaccination
~~ rarely protective
~~ generally suppressive

Controled Marketing
~~ for recoverd countries

Depopulation
~~ infected populations

Education and Cooperation
~~ between veterinary and human health agencies
AI VACCINE OPTIONS 4: Incactivated Homologous Strains
- H5N1?

Inactivated heterologous strains
- H5N2

Recombinant Vaccines
- vector viruses + H5

Reverse Genetics
AI VACCINATION ADVANTAGES FOUR: Reduces susceptibility to infection

Increases neccessary infective dose

Vaccinated Birds shed less virus
- decreased contamination of the environment
- decreased risk of human infections

Compliments Culling
- slows spread of virus
- must be used stragetically
AI VACCINATION DISADVANTAGES FOUR: Not in line wtih OIE or EU control stategies
- this may change
- Russia could care less

Negative impact on trade agreements

Clinical signs are reduced
- disease may be missed in a flock

Vaccinated and naturally infected birds can be difficult distinguish
AI CONTROL MEASURES FIVE: Culling of infected or in contact poultry
- not wild birds

Biosecurity of poultry operations
- all in / all out
- quarantine
- hygiene

Protection and surveillance zones around wild bird refuges

Improve veterinary infrastructure

Treatement and vaccination
- people
- poultry?
H5N1 7 CONSEQUENCES: Embargo on poultry and poultry products from affected countries

Poultry sales falling
- 50% in some countries

Culling
- 200 M domestics so far

Livelihood of Farmers
- 300 M affected

Public Panic
- zoo closures
- dead birds dumped
~~ garbage cans
~~ streets
~~ Nile

Cost to Global Poultry Industry
- > 10 B USD

Cost of Surveilance of Wild Birds
- $7.4 M Alaska
- $3.6 M Canada
-
H5N1 IMPENDING PANDEMIC COST: $4 T

2% of Global Economy
H5N1 4 ROUTES INTO CANADA: Wild Bird Migration

Illegal and legal Trade
- poultry and products
- pet and captive birds
- fighting cocks
- mammals
~~ wet markets

Movement
- infected people
- fomites

Aerosol
H5N1 FOUR PANDEMIC PONDERANCES: Could we be blinded by the severity of the HPAI virus in poultry in thinking it would be the next pandemic strain when the actual risk omay be LPAI of various subtypes

Each year up to 500,000 people die of seasonal influenza infections. HFN1 has been circulatiing for 10 years and has caused 98 deaths

From 2003-2006 9.1 million people were infected with HIV/AIDS, according to UN AIDS and U.S. Dept of Health and Human Services
- so why the big deal about AI?

WHO: bird fule pose a greater threat than any infectious human disease, including HIV/AIDS and SARS
- but you get to have a great concert afterwards

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Deck Info

Number of cards 166