Flying flu particles mean a fan could help beat virus
A fan and a humidifier may be more helpful than a face mask to prevent flu spreading around a household.
That was the conclusion researchers came to after finding half of flu infection cases in families were caused by the transmission of fine respiratory droplets known as "aerosol", which cannot be avoided by wearing masks or washing hands.
"The importance of aerosol transmission implies that the possible control strategies to prevent the spread of influenza within households may need to be reconsidered," said Dr Ben Cowling, associate professor of Hong Kong University's school of public health, who led the research.
Researchers studied 275 families in Hong Kong and 507 families in Bangkok, with family members randomly allocated to wash their hands and wear masks to try to stop the flu spreading.
Half of these relatives still became infected through "aerosol", which are infectious droplets emitted through the nose with a diameter below 5 microns - 200 times smaller than a millimetre - that can remain airborne for relatively long periods.
Larger infectious droplets settle within 2 metres of the source and can be avoided by wearing masks and hand-washing.
Cowling said better ventilation and home humidification in the flu season could reduce aerosol in the air and with it the risk of catching the virus. However, he said vaccination remained the best preventive option.