Force of infection

In epidemiology, force of infection (denoted $\lambda$ ) is the rate at which

infectious disease.^[1] Because it takes account of susceptibility it can be used to compare the rate of transmission between different groups of the population

for the same infectious disease, or even between different infectious diseases. That is to say,

\lambda

is directly proportional to

\beta

; the effective

transmission

rate.

\lambda ={\frac {\mbox{number of new infections}}{{\mbox{number of susceptible persons exposed}}\times {\mbox{average duration of exposure}}}}

Such a calculation is difficult because not all new infections are reported, and it is often difficult to know how many susceptibles were exposed. However, $\lambda$ can be calculated for an infectious disease in an

pyramid

, is assumed. In this case,

\lambda

is given by:

\lambda ={\frac {1}{A}}

where $A$ is the average age of infection. In other words, $A$ is the average time spent in the susceptible group before becoming infected. The rate of becoming infected ( $\lambda$ ) is therefore $1/A$ (since rate is 1/time). The advantage of this method of calculating $\lambda$ is that data on the average age of infection is very easily obtainable, even if not all cases of the disease are reported.^[citation needed]

References

PMID 19765352
.

Further reading

Muench, H. (1934) Derivation of rates from summation data by the catalytic curve. Journal of the American Statistical Association, 29: 25–38.

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[75years-1] PMID 19765352
.

[1]

See also

References

Further reading