PMC:3463543 / 24517-27046 JSONTXT

{"project":"2_test","denotations":[{"id":"23056454-21097384-92972571","span":{"begin":444,"end":445},"obj":"21097384"},{"id":"23056454-17182688-92972572","span":{"begin":449,"end":451},"obj":"17182688"},{"id":"23056454-21097384-92972573","span":{"begin":490,"end":491},"obj":"21097384"},{"id":"23056454-15737154-92972574","span":{"begin":1283,"end":1285},"obj":"15737154"},{"id":"23056454-21300628-92972575","span":{"begin":1289,"end":1291},"obj":"21300628"},{"id":"23056454-21731764-92972576","span":{"begin":1512,"end":1514},"obj":"21731764"},{"id":"23056454-18367530-92972577","span":{"begin":1743,"end":1745},"obj":"18367530"},{"id":"23056454-21731764-92972578","span":{"begin":2107,"end":2109},"obj":"21731764"},{"id":"23056454-18367530-92972579","span":{"begin":2197,"end":2199},"obj":"18367530"},{"id":"23056454-20025197-92972580","span":{"begin":2203,"end":2205},"obj":"20025197"},{"id":"23056454-18628983-92972581","span":{"begin":2349,"end":2351},"obj":"18628983"}],"text":"Implications for Influenza’s Transmission Patterns\nMany mechanisms have been proposed to explain influenza’s seasonality, including (1) environmental and climatic factors (e.g., temperature, relative or absolute humidity, and solar intensity), (2) host behavioral changes (e.g., school schedule and increased crowding during winter or rainy seasons), and (3) oscillations in host immunocompetence (e.g., vitamin D levels and melatonin levels) [7], [35]. A recent review by Tamerius et al. [7] assesses the feasibility of various mechanisms and concludes that the central questions in influenza seasonality remain unresolved. Our study was designed to focus on the effect of humidity, and we conducted all experiments at room temperature. In indoor environments, where infection is more likely to occur due to the much larger amount of time spent there and the greater spatial density of potential hosts, temperature tends to fall in a narrow range around 20°C. With this restriction, we were not able to distinguish between the effects of relative v. absolute humidity.\nOur findings in human mucus could help explain, at least in part, the transmission patterns of influenza. In temperate regions, wintertime heating reduces RH in the indoor environment to low levels, usually \u003c40% [36], [37]. Low RHs not only help preserve the viability of IAV but also enable IAV carrier aerosols to persist longer in air because of their smaller size and lower settling velocities that result from more vigorous evaporation [16]. Thus, transmission of influenza in temperate regions could be enhanced in winter primarily via the aerosol route. In tropical regions, high temperatures may suppress transmission, particularly through the aerosol route [38], [39]. However, lower temperatures and near-saturated RH during the rainy season create an opportunity for transmission via different mechanisms for large droplets v. very small aerosols. Large droplets would settle more quickly due to gravitation because they do not shrink as much at ∼100% RH (only to 93% of their original diameters at 99% RH, and 76% at 98% RH [16]). Once settled on a surface, they may serve as a reservoir for contract transmission [39], [40] since IAV is well preserved at ∼100% RH, as shown in this study. On the other hand, submicron aerosols such as those exhaled in human breath [41] would remain aloft, and thanks to the lower temperatures and suitable RHs for survival, transmission by these submicron droplets via the aerosol route might still be effective."}