Background: Consultation waiting rooms and similar medical settings, either public or private, are places where children have higher probability of acquiring some infectious diseases, especially during outbreaks.
Methods: During a measles outbreak which occurred in Lisbon in 1989 a case-control study was carried out in a major paediatric hospital to estimate the risk of measles infection associated with the exposure in medical settings. The statistical analysis was performed with data matched on age, using conditional logistic regression, to reach a multivariate model which explains the risk in the presence of the main variables of interest.
Results: The crude odds ratio (OR), based upon 72 cases and 216 controls, in children younger than 12 years, was 4.1 (P < 0.001). Hospital emergency settings had an OR of 4.9 (P < 0.001) and private physicians' offices an OR of 1.4 (P = 0.689). Non-whites showed a 2.4-fold increase in the crude probability of getting measles, although this was not statistically significant (P = 0.118). Children who had a recent contact with cases of measles had an OR of 14.7 (P = 0.005). Immunization against measles was an important protective factor (OR = 0.1; P < 0.001), as was attendance at kindergartens or wet nurses, although less significant (OR = 0.4; P = 0.051).
Conclusions: This study supports the need for children to avoid unnecessary exposure in medical settings during measles outbreaks, especially if those settings are crowded and result in long waiting periods before a consultation.