In two communities of similar size and age structure (A and B) there were outbre

Question

In two communities of similar size and age structure (A and B) there were outbreaks of viral illness (virus A in community A and virus B in community B), both of which were traced back to a single source. Exposure to these viruses in each community confers permanent immunity. In community A, 200 susceptible people were exposed to an index case, 150 people were infected (not including the index case), 75 people became ill, and 40 people died. In community B, pathogenicity was 40%, infectivity was 90% and virulence was 60%.

Which virus had the greatest infectivity?

Which virus was most pathogenic?

Which virus was most virulent?

Explanation / Answer

1).

In the community A, 150 people out of 200 are infected. Means, the percent infectivity is, 75%. In community B, the infectivity is given as 90%. Thus, the virus B has greater infectivity than the virus A.

2).

In the community A, 75 people out of 150 are infected. Means, the percent pathogenicity is, 50%. In community B, the pathogenicity is given as 40%. Thus, the virus A has greater pathogenicity than the virus B.

3). Assuming that the virulence is indicated by the death of people, the virulence of virus is, 53.3% (40 in 75). While the virulence of virus B is, 60%. Thus, the virulence of virus B is greater thatn virus A.

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