Term
| What is the difference between the "incubation period" of a virus and the "latent period"? |
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Definition
1) Incubation refers to time from exposure to disease
2) Latent refers to period of infection without being infectious (i.e. until you can pass it on). |
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Term
| When does an epidemic become an endemic or pandemic? |
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Definition
Endemics are epidemics that remain stable for long periods of time.
Pandemics are global outbreaks (Ro>1 may predispose this) |
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Term
| What is the "incidence rate"? |
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Definition
#cases/population at risk over time
ex) 20 cases/ (500 beds) (30 days per month)= 0.00153 cases/patient-day |
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Term
| What is the difference between incidence and prevalence? |
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Definition
Incidence in new cases in given population over time period
Prevalence is total number of disease cases/total people in population of interest. |
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Term
There is a disease with an attack rate of 0.2, k=5 and D= 5 days.
What is the Ro and how do you interpret it? |
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Definition
Ro= bkD= 5
Remember, attack rate is proportion of those exposed who become ill to total exposed
Ro>1 means there is an ever increasing number of infected individuals causing epidemic or pandemic (influenza or SARS) |
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Term
| What is the Case Fatality Rate? |
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Definition
proportion of infected individuals who die
ex) CFR or rabies is 100%, but CFR or Hep A is only 0.5% |
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Term
| WHat is Zoonosis and how does it relate to SARS and West Nile? |
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Definition
Passage from vertebrate animals to man.
SARS goes from bat to pig to man
West Nile goes from mosquitto to pig to human. |
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Term
| What is the relationship between Ro and endemic status? |
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Definition
| Ro= 1 means that there is a stable number of individuals who are infected with every new generation, which is, by definition, an endemic (West Nile is an example) |
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Term
| What does it mean for a Herd Immunity Threshold to be higher than the Ro? |
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Definition
Means the fraction of the population that is immune to a virus is great enough to prevent an outbreak beyond one index case.
The higher the Ro, the greater the HIT needed. |
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Term
| When investigating an outbreak, which 4 factors should you determine? |
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Definition
1) Reservoir
2) Transmission route
3) Incubation time
4) Ro value. |
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Term
| Characterize a basic Norovirus infection. |
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Definition
1) RNA virus with unenveloped capsid
2) Self-limited (24-48 hours) with nausea, vomiting and abdominal pain (Ro <1)
3) Very contagious
4) Human resevoir with oral-recal route |
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Term
| What is significant about the fact that Norovirus is not reactive to Soap? |
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Definition
| It is not an enveloped virus (therefore it is more stable and harder to target) |
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Term
| How can you treat Norovirus? |
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Definition
You can't!
Prevent with washing hands (mechanical not chemical effect) and harsh chemical cleaning of enviornment. |
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Term
| What are different causes of acute Pneumonia? |
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Definition
1) Typical Bacterial= Strep. pneumoniae
2) Atypical Bacterial= Chlamidiae, Legionella, Mycoplasma
3) Viral= Influenza, Adenovirus, RSV, Metapneumonia |
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Term
| Explain the basic characteristics of a SARS infection. |
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Definition
1) Enveloped RNA virus that is stable in feces and urine (1-4 days) with a SHORT incubation time.
2) Reservoir is fruit bats which is picked up by animals and transferred to humans (or directly through bat droppings).
3) High mortality (10%) |
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Term
| Which H strains of influenza cause Avian influenza and how does it occur in humans? |
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Definition
1) H5, H7 and H9, which normally have low pathogenicity and are carried asymptomatically in GI of birds. HPAI cause disseminated disease (H5N1 has 58% mortality!)
2) H5N1 reassortment through antigenic shifts have increased the Ro>1 and expanded host range.
3) Resistant to Amantadine and Rimantadine, as well as Oseltamivir sometimes! |
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Term
| Explain the emergence of vCJD. |
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Definition
Spongiform encephalopathy that is caused by abnormal (dead) prion proteins.
1) Sporadic is most common (89%), with Familial (10%) and Infective (1%) less common.
2) Uniformly fatal and arises from consumption of BSE meat, or sporadically |
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Term
A patient presents with encephalitis in Malaysia after coming into contact with pigs that have been eating fruit bat droppings.
What is going on? |
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Definition
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Term
| How was Metapneumovirus discovered? |
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Definition
| PCR "fishing" of children with undiagnosed pneumonias. |
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Term
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Definition
| Dengue-like (fever, bone pain and rash) is Asia and Italy (outbreak) that is likely caused by the effects of global warming on mosquito migration northward. |
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Term
| Why have Pertussus, Measles and Polio all started to re-emerge in isolated communities? |
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Definition
| Vaccine-Preventable conditions where people refuse to take them! |
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Term
| Why is Salmonella infection on the rise? |
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Definition
Current meat processing approaches.
Gram (-) bacterium which is a zoonosis without host specificity. |
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Term
| What are 5 important factors in emerging infections? |
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Definition
1) Interspecies crossing (birds/bats/pigs) in Avian influenza and SARS
2) Adaptation of virus to human host (SARS and HIV)
3) Susceptible hosts (travel and antigenic shift)
4) Global warming (Chikungunya and Dengue)
5) Improved diagnostic tests (Metapneumovirus) |
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