Weather experts are studying swine flu to see if climate could influence its spread and severity.
Determining the impact of cold, heat, dryness and humidity on the H1N1 strain -- which has killed up to 149 people in Mexico and had milder effects elsewhere -- could illuminate the countries and regions most vulnerable to infection.
Climate information may also provide clues into whether the virus is likely to return year after year on a seasonal basis.
Following are details about seasonality of regular flu, and the weather and other factors affecting its patterns, according to data from the World Health Organisation, World Meteorological Organisation, and leading scientists:
Cold And Dryness
Flu incidence peaks in the winter season in temperate parts of the world, generally described as areas outside the tropics.
Cold and dry conditions help the virus survive outside the body, meaning that droplet particles take longer to evaporate and remain airborne for more extended periods in winter.
Heat And Humidity
Influenza outbreaks do occur in the tropics, though less frequently than in areas with less heat and humidity, and without the seasonality seen in areas with wintry weather.
Poor laboratory and health data, especially from Africa and Latin America, have made it difficult for international experts to track viral transmission in tropical regions.
School Cycles
School cycles have also been shown to affect the seasonality of flu. Winter school breaks tend to reduce flu transmission to children by as much as 25 percent, mainly because they provide fewer opportunities for the virus to spread among large groups.
Other Factors
The precise strain of virus circulating, which can change from flu season to flu season, can also affect how virulent it is and how many people may fall ill in a given outbreak. The levels of immunity in the population, vaccination programmes, hygiene practices and other practices also play a role.
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It is quite well documented that flu season hits when people's Vit D reserves become depleted, ie during the low-light Winter months,when people aren't receiving enough strong sunlight to produce their own Vit D.
Also to be considered are the increasing amounts of GM foods which have been scientifically shown to disrupt the gut bacteria and immunological responses, not to mention the health concern from the pesticides that accompany GM food production.
An additional factor to consider with GM lifeforms:
According to Jeffrey Smith (author of Genetic Roulette), environmental/weather is just one factor that seems to affect transgene expression (which traits are turned on/off in different scenarios) and may differ from plant to plant and even within different parts of the same plant. Gene expression will vary markedly from season to season and location to location as the plant tries to adapt.
Is it a stretch to suspect that bio-engineered viruses, which most likely lack homogeneity as well, would have similar unpredictable virulence (transgene expression) in different environments, climates or even populations?