Review of 26 years' hospital admissions for chickenpox in North London.

The epidemiology of chickenpox admissions to an Infectious Diseases Unit was studied over 26 years. Risk factors, markers of disease severity, and complications were analysed in patients admitted during the last 5 years. Some 613 patients were admitted with chickenpox over three 5-year periods between 1968 and 1993. There was a 2.23-fold increase in the number of adults admitted from home between the first and last period. Patients of European origin showed a three-fold increase. The mean age of adults rose from 26.2 to 34.3 years. Some 23% of adults had varicella pneumonitis. Smokers were six times more susceptible to pneumonitis than were non-smokers. Adult asthmatics were not at increased risk, whereas 42% of asthmatic children had chest complications. Seventeen of the 18 immunocompromised patients had a relatively uncomplicated course. Of the children, 32% had secondary skin infections, with no excess complications among those with eczema. Thrombocytopenia and elevated aspartate transaminases were four times and twice, more frequent in adults than children, respectively. These features occurred mostly in males. The male-to-female admission ratio was 2:1 in adults, and 1.2:1 in children. Males in both age groups showed a trend to more severe disease and more primary complications than did females. Our data showed an increase in adult chickenpox admissions. We have identified asthma as a risk factor for pulmonary complications in children, but not adults, and male gender as an independent risk factor for severe chickenpox.