Why does the flu virus proliferate in winter?

Influenza A structure

The H5N1 avian influenza virus thrives during the cold season from October to March, corresponding to the peak activity period of normal human influenza viruses.

Experts are concerned that the bird flu virus in humans and chickens will "mate" in a "mixed host" (meaning that it can infect both viruses, such as humans or pigs) to produce one. Fierce hybrids are capable of easily spreading from person to person and are capable of killing millions of people around the world.

The question is, why does the peak of the flu often fall during this time of year? Scientists believe that there are countless explanations for this, from the "more comfortable" live virus in the cool and humid environment until people often gather during the festive season, enabling the virus to proliferate.

Last year, an Asian science group published in Nature that the H5N1 virus has been active in China since 2001 in a seasonal pattern, culminating in the October-March period, when the central temperature The average is less than 20 degrees Celsius. Especially the lower the temperature, the better the virus lives.

"When the temperature was below 20 degrees Celsius, the isolation rate of H5N1 increased by 15% in waterfowl," said Yuen Kwok-yung, Hong Kong's leading scientist in the fight against SARS and bird flu. Isolation rate is the amount of virus present in patient samples such as blood and waste.

Waterfowl are considered a natural reservoir of H5N1, helping the virus first jump to people in Hong Kong in 1997, killing 6 people. Since late 2003, the virus has caused a pandemic in the poultry world in many Asian countries and killed at least 62 people. In the past few weeks, viruses have appeared in Europe, including Russia, Turkey and Romania. Many experts believe that the cause is caused by migratory birds.

Flu virus through a microscope

Samson Wong, a microbiologist at Hong Kong University, said the bird flu virus can live up to four days in water at temperatures of about 22 degrees Celsius. At 0 degrees Celsius, they can survive for more than 30 days. This virus can also last longer in moist environments on water droplets and waste from the body.

Dr Malik Peiris from Hong Kong University said "the virus does not reproduce outside the host. Through soil contamination and feces, the virus can still survive until it can be transferred from object to object. Other strong development of the virus may be related to human density and intimacy between people in the cold season, or the movement of closed-door media to keep heat in. summer in the cold season ".

Another reason is that ultraviolet rays decrease in the winter. According to Alan Hampson, advising the Australian government in preparing for pandemic flu, ultraviolet rays have the ability to disable viruses and bacteria."However, ultraviolet light alone is not enough to explain. It can only be a constituent. There is moisture and temperature that determine whether the virus can last in the environment," Hampson said. strong.

My Linh (according to Reuters)