Researchers discover more details about how outdoor temperature and flu outbreaks are linked.
According to calculations, a cold week with an average temperature below zero degree Celsius precedes the start of the flu epidemic.
Nicklas Sundell, a researcher at Sahlgrenska Academy and infectious diseases specialist at Sahlgrenska University Hospital, conducted a study on this subject, and looked at 20,000 virus samples taken with nasal swabs from people who sought medical care in the Gothenburg area. The incidence of respiratory viruses was then compared over time with weather data from the Swedish Meteorological and Hydrological Institute (SMHI) and the results are clear: Flu outbreaks seem to be activated about one week after the first really cold period with low outdoor temperatures and low humidity.
“We believe that this sudden drop in temperature contributes to “kickstart” the epidemic. Once the epidemic has started, it continues even if temperatures rise. Once people are sick and contagious, many more may become infected,” says Nicklas Sundell.
The study supports the theory that aerosol particles containing virus and liquid are more able to spread in cold and dry weather. If the surrounding air is dry, it absorbs moisture and the aerosol particles shrink and can remain airborne.