Flashcards in 02/27a Introduction to Virology Deck (15)
What is the broad, general class of viruses that presently pose a serious public health issue? What specific viruses are included in this class
'New' or 'emerging' viral diseases
West Nile encephalitis
What types of global socio-economic and environmental factors contribute to the emergence of new viruses? Name six
Social upheaval and warfare
Trade, travel, emigration
Close contact with carrier species (animals)
What huge viral pandemic is illustrative of the various factors that contribute to emerging viruses?
Influenza pandemic of 1918
What three factors made the Spanish flu so deadly?
1) Caused excessive inflammation - cytokine storm
2) Secondary bacterial infections
3) Was entirely new to human populations
Why was polio endemic and not epidemic to the United States until the 1850s?
Lack of hygiene led to constant exposure and thus immunity to poliovirus
Advent of hygiene led to large populations that did not have immunity
What four things are necessary to eradicate a virus?
1) Political will exists
2) A vaccine is available
3) No animal reservoir exists
4) Elimination of the agent from the environment can be certified
What makes emerging viruses so deadly?
There is no "balance" established between pathogen and host to optimize viral replication and spread
Thus there is massive mortality as the host learns to deal with the new threat
For this reason, "old" viruses are often less deadly
From what primate species did HIV cross over to infect humans?
Chimpanzees (pan troglodytes)
What is the cause of the high incidence of Hepatitis C virus in Egypt?
Rise in cases of schistosomiasis in Egypt after the construction of the Aswan dam lead to a very vigorous eradication campaign
Unfortunately the IV injections were frequently carried out with non-sterile needles
This lead to the epidemic spread of HCV
Why is HCV such a health concern?
Causes a high rate of chronic hepatitis
Currently the leading indication for liver transplantation in the US
What is one hypothesis that explains why West Nile virus caused fatalities in the United States, while it is endemic and relatively harmless to other areas?
Combination of vector species - US strain represents a mix of mosquito species, resulting in a mosquito strain that prefers urban environments and requires a blood meal for egg development, and thus pose a threat to humans
What is special and unusual about the SARS pandemic?
It was spurred by globalization, and spread rapidly via global airline travel
Why didn't SARS cause the devastation of the Spanish flu?
1) Relatively stable socio-economic circumstances
2) Rapid implementation of "old-fashioned" containment methods (isolation, quarantine, etc.)
3) SARS has a slow transmission and long incubation compared to the Spanish flu
4) SARS has relatively inefficient transmission - most cases were traceable to just a few people
What factors favor a host range expansion and pandemic spread of influenza? Name five
Travel, trade, and migration
Close contact with carrier species (bird markets)
Poverty and poor health care systems
Urbanization/densely populated areas