Human influenza infections exhibit a strong seasonal cycle in temperate regions. Recent laboratory and epidemiological evidence suggests that low specific humidity conditions facilitate the airborne survival and transmission of the influenza virus in temperate regions, resulting in annual winter epidemics. However, this relationship is unlikely to account for the epidemiology of influenza in tropical and subtropical regions where epidemics often occur during the rainy season or transmit year-round without a well-defined season. We assessed the role of specific humidity and other local climatic variables on influenza virus seasonality by modeling epidemiological and climatic information from 78 study sites sampled globally. We substantiated that there are two types of environmental conditions associated with seasonal influenza epidemics: “cold-dry” and “humid-rainy”. For sites where monthly average specific humidity or temperature decreases below thresholds of approximately 11–12 g/kg and 18–21°C during the year, influenza activity peaks during the cold-dry season (i.e., winter) when specific humidity and temperature are at minimal levels. For sites where specific humidity and temperature do not decrease below these thresholds, seasonal influenza activity is more likely to peak in months when average precipitation totals are maximal and greater than 150 mm per month. These findings provide a simple climate-based model rooted in empirical data that accounts for the diversity of seasonal influenza patterns observed across temperate, subtropical and tropical climates.
Influenza viruses are genetically diverse owing to high mutation rates, frequent reassortment among genomic segments and their tendency to jump between hosts. Three studies describe new modelling approaches to analyse and predict influenza virus evolution and also shed light on the origin and spread of currently circulating viruses.
Back in June, we heard of a controversial study conducted by a team of University of Wisconsin-Madison researchers that generated an influenza virus with similar characteristics to the infamous 1918 pandemic flu virus. The research was criticized by many and branded as crazy, foolish and dangerous by experts.
Influenza A jumped from horse to camel Futurity: Research News Although there is no immediate risk, the inter-mammalian transmission of the virus is a major concern for public health researchers interested in controlling the threat of pandemic...