Evidence of a causal role of winter virus infection during infancy in early childhood asthma.

Wu et al studied over 95,000 infants born between 1995 and 2000 and followed through 2005 who were enrolled in the Tennessee Medicaid programme from birth through to early childhood. Among 95,310 children studied, infant birth approximately 4 months before the winter virus peak carried the highest risk, with a 29% increase in odds of developing asthma compared with birth 12 months before the peak (adjusted odds ratio, 1.29; 95% confidence interval, 1.19–1.40). Infant age at the winter virus peak was comparable to or greater than other known risk factors for asthma. Am J Respir Crit Care Med. 2008;178:1123-9.