What is the definition of virus epidemiology?
The study of determinants, frequency, dynamics, and distribution of viral diseases
What is the risk of infection/disease in an animal or animal population determined by?
- Characteristics of the virus (genetic variation)
- The host and host population (Passive, innate, and required resistance)
- Behavioral, environmental, and ecological factors that affect virus transmission from one host to another
What do viral epidemiologist investigate/study?
Distribution, determinants, dynamics, and frequency of viral pathogens
Also factors that affect host susceptibility, impacts of the dz on the health, finances, economy/society of the endemic area
As well as vaccine testing/drug trials for pathogens
What is the case fatality rate?
The number (%) of deaths among clinically ill animals
(animals that have died/clinically sick animals) X 100
*based on outcome of dz population
What is the mortality rate?
The number (%) of animals in a population that die from a particular dz over a specific period of time
(animals that have died/total animal population) X 100
*based on outcome of dz in population
What is the morbidity rate?
The morbidity rate is the percentage of animals in population that develop clinical signs attributed to a particular virus over a defined period of time
What is incidence?
The number of new cases that occur in a population over a specified time
*these refer to acute, short lasting dz
What is prevalence?
The number of occurrences of dz (old and new), infection, or related attributes in a population at a particular point of time
What does sporadic viral dz refer to?
Viral diseases occuring occasionally, individually, or in scattered instances, and in an irregular and haphazard manner
What does enzootic viral diseases refer to?
The constant presence of a viral disease within a given geographic area or population group
(endemic in humans)
What does epizootic viral diseases refer to?
The occurrence of more cases of viral diseases than expected in a given area or among a specific group of animals over a particular period of time. Refers to peaks in dz incidence that exceed the enzootic baseline or expected incidence of dz
(Epidemic in humans)
What does panzootic viral dz refer to?
A virus epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population
(pandemic in humans)
What is an asymptomatic carrier?
Animals that have contracted an infectious viral dz, but display no clinical signs
They may shed virus continuously or intermittently
When do incubatory asymptomatic carries shed virus?
During the incubation phase
What are inapparent carriers?
Patients that carry a virus but never at any stage, show clinical signs
What are convalescent or chronic carriers?
Animals that shed virus during recovering from dz
What is a contagious dz?
A dz that is spread from one person or organism to another by direct or indirect contact
What is the period of contagiousness?
The time during which an infected animal sheds virus
What is an exotic dz?
A dz not known to occur in a particular country or geographic area
T/F: Reservoirs always living creatures
Can be animate or inanimate
Rabies has never been reported before in St. Kitts. Suddenly, a few cases of canine rabies are reported from St. Kitts, especially from Ross students with dogs that accompanied them from the US. In this context, Rabies would be a _________ dz in St. Kitts
What is seroepidemiology?
the use of serological data as the basis of epidemiologial investigation, as determined by diagnosing serological techniques
What is molecular epidemiology?
The use of moleular biological data as the basis of epidemiological investigation of viral diseases
How are most viral dz transmitted?
Direct contact is most common
What are some horizontal routes of transmission?
Contact: Direct:bites, sex, licking, **droplet - aerosol less than one meter) - Indirect: airborne/fomites
Vector transmission: mechanical, biological
What is vertical transmission?
Transmission from mother to embryo, fetus, or neonate
*before, during, or shortly after parturition
What are arboviruses?
A class of viruses transmitted to humans by arthropods such as mosquitoes and ticks
What are the transmission cycles of arboviruses?
Enzootic (Sylvatic/Jungle): The natural transmission of virus between wild animals/birds (vertebrate hosts) and primary insect vectors
Epizootic (Rural): The virus is transmitted between non-wild/domestic animals and the primary or accessory insect vectors
Urban cycle: The virus cycles between humans and insect vectors
What is an amplifying host?
Host in which the level of a virus can become high enough that an insect vector such as a mosquito that feeds on it will probably become infected
What is a dead end or incidental host?
A host from which infectious agents are not transmitted to other susceptible hosts. They do not develop sufficient viremia to be picked up by insect vectors
What are some common vehicle transmission pathways?
Fecal contamination of food and water supplies –> fecal oral route
Virus contaminated meat or bone products (ex: classical swine fever)
What is iatrogenic transmission?
Infection that is transferred during medical or surgical practice. This happens in 2 ways:
- Introductions of pathogens by contaminated instruments or contaminated body surface
- Introduction of pathogen through contaminated prophylactic or therapeutic preparations (ex: presence of porcine circovirus genome in rotavirus vaccine)
What is a nonsocomial mode of transmission?
Occurs while an animals is in a veterinary hospital or clinic (aka hospital acquired infection)
T/F: The term zoonosis is used to describe infections that are transmissible from humans to animals
From animals to humans
Which virus is more stable: a virus transmitted through respiratory route or a virus transmitted through fecal-oral route?
Virus via fecal-oral route is more stable
*fecal-oral virus needs to survive in feces (environment)
Which virus is more stable in the environment: Naked or enveloped?
What is the concept of herd immunity?
A form of immunity that occurs when the vaccination of a significantly large portion of a population provides a measure of protection for individuals who have not developed immunity
What is the typical course of an infectious dz?
Incubation period Prodromal period Acute period Decline period Convalescent period
T/F: The incubation period refers to the interval between infection and the onset of clinical signs
*in many diseases there is a period during which animals are infectious before they become sick
What is the prodromal period of a virus?
The first signs and feelings of illness after incubation period. The period of early symptoms of a dz occurring after the incubation period and just before the appearance of the characteristic symptoms of the dz
What is the period that is characteristically at the height of the disease?
Acute period - there will be severe clinical signs
T/F: the decline period is described at the period of time when clinical signs become chronic
The period when clinical signs begin to subside is the DECLINE phase
What is the convalescent period?
When the body gradually returns to its pre-diseased state and health is restored
T/F: Hospital acquired infection is also known as nosocomial transmission
T/F: Enteric viruses have been shown to be more stable in the environment than respiratory viruses