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?

Answer 1

Which virus had the greatest infectivity? Virus B 90%

Which virus was most pathogenic? Virus A 50%

Which virus was most virulent? Virus B 60%

Step-by-step explanation:

In order to answer this question, it is necessary to understand these 3 epidemiological terms.

Infectivity is the ability of an organism to invade a host.

It is calculated by the formula

Individuals infected divided by Individuals susceptible X100

`(150)/(200) X100` = 75% (Compare with Virus B 90%)

Pathogenicity is the ability of an organism to cause disease.

It is calculated by the formula

Number of individuals with clinical disease divided by Number of individuals infected X100

Therefore the pathogenicity of virus in community A is

`(75)/(150) X100` = 50% pathogenicity (Compare with virus B 40%)

Virulency is the ability of an organism to cause death.

It is calculated by the formula

Individuals who passed away divided by Individuals with disease X100

`(40)/(75) X100` = 53.33% (Compare with virus B 60%)

QUESTIONS:

Which virus had the greatest infectivity? Virus B 90%

Which virus was most pathogenic? Virus A 50%

Which virus was most virulent? Virus B 60%