Question

In 1990, a large measles outbreak occurred in Philadelphia in predominantly unvaccinated preschool children. There were 892 unvaccinated children identified with 486 cases of measles of which 6 died. 1. Calculate the attack rate (show the formula, decimal point calculation, and response in %). 2. Calculate the case fatality rate (show the formula, decimal point calculation, and response in %).

Answer 1

This is a simple problem related to finding the rate of attack and rate of fatality in a given scenario of measles in unvaccinated children.

Now let us collate the given information first.

Total number of children who were unvaccinated =892

Total number of measles affected children =486

Total number of children who died =6

1. The attack rate is defined as the proportion of the children who got infected from the lot of all unvaccinated children.

Mathematically,

Attack rate =cases of infection of measles/ Total cases of unvaccinated children

=486/892

=0.5448 or 54.48 %

Thus we can say that the attack rate or rate at which the children are getting affected by measles is 54.48 %

2.

The fatality rate is defined as the proportion of the children who died from the lot of all unvaccinated children.

Mathematically,

Fatality rate =cases of fatality due to measles/ Total cases of unvaccinated children

=6/892

=0.006726 or 0.6726 %

Thus we can say that the fatality rate or rate at which the children are dying due to measles is 0.6726 %