Size of infecting dose may be important

Editor—In describing severe measles one of us (DCM) made the error of linking the severity directly with the state of nutrition of the child when he or she contracted measles.1 Several studies have since convincingly shown that the state of nutrition is unimportant, although vitamin A deficiency may play some part. The severity of measles was related to the degree of exposure, which was presumably related to the size of the infecting dose.2 Analysis of patients' records from a severe outbreak of measles in Copenhagen in the past showed a similar finding.3 Perhaps the size of dose may vary with the nutritional state of the child passing on the infection.

In his editorial Greg Hussey did not mention these findings.4 If the case fatality rate and the severity vary by more than 100-fold between west Africa and Europe this should be worthy of further research to identify whether the degree of exposure and the size of the infecting dose are important in other infections. Perhaps people working in veterinary medicine may be able to help.

Should health workers in developing countries advise mothers to keep other, particularly small children, in separate beds (and where possible in separate rooms) from children who may be incubating or in the early stages of measles and possibly other infections? In Guinea-Bissau it was found that the number of people in the bed was a risk factor for childhood mortality (mortality ratio 1.37 (95% confidence interval 1.04 to 1.81)) when …