Influenza and humidity--Why a bit more damp may be good for you!

Influenza viruses cause much winter-time morbidity and death in temperate regions. We still do not understand why 'flu is more common in winter. Since the 1960s, investigators have studied the role of relative humidity and temperature on viral survival, transmission and infection rates but results have demonstrated only inconclusive trends. Over the past few years however, a series of exciting studies have instead focussed on absolute humidity and demonstrated highly significant correlations with viral survival and transmission rates in both laboratory and epidemiological models. Here we review the evidence for a causal association between absolute humidity and 'flu transmission and outline how this could lead to a new approach to curbing this and perhaps other viral epidemics in the winter months.

Streptococcus pneumoniae carriage prevalence in Nepal: evaluation of a method for delayed transport of samples from remote regions and implications for vaccine implementation.

BACKGROUND: Pneumococcal disease is a significant cause of morbidity and mortality in young children in Nepal, and currently available pneumococcal conjugate vaccines offer moderate coverage of invasive disease isolates. METHODS: A prevalence study of children aged 1.5 to 24 months in urban and rural Nepal was conducted. In the urban group, nasopharyngeal swabs (NPS) were transported using silica desiccant packages (SDP) with delayed processing (2 weeks), or skim-milk-tryptone-glucose-glycerin (STGG) with immediate processing (within 8 hours). Pneumococcal nasopharyngeal carriage prevalence, serogroup/type distribution and isolate genotypes (as defined by multilocus sequence typing) were determined. RESULTS: 1101 children were enrolled into the study: 574 in the urban group and 527 in the rural group. Overall carriage prevalence based on culture from specimens transported and stored in STGG was 58.7% (337/574), compared to 40.9% (235/574) in SDP. There was concordance of detection of pneumococcus in 67% of samples. Using the SDP method, pneumococcal carriage prevalence was higher in the rural population (69.2%; 364/526) compared to the urban population (40.9%; 235/574). Serogroup/type distribution varied with geographical location. Over half of the genotypes identified in both the urban and rural pneumococcal populations were novel. CONCLUSION: The combination of delayed culture and transport using SDP underestimates the prevalence of pneumococcal carriage; however, in remote areas, this method could still provide a useful estimate of carriage prevalence and serogroup/type distribution. Vaccine impact is unpredictable in a setting with novel genotypes and limited serotype coverage as described here. Consequently, continued surveillance of pneumococcal isolates from carriage and disease in Nepali children following the planned introduction of pneumococcal conjugate vaccines introduction will be essential.