Research on guinea pigs (literally) has shown why there's a seasonal influence. Two groups of guinea pigs, one infected with a flulike germ, one not, each in cages relatively close together in a room.
At 5 degrees Celsius all the healthy guinea pigs got the Guinea pig flu.
At 20 degrees only one out of 4 got the flu.
At 30 degrees none got the flu (and they were all living as well
)
Weirdly enough, during winter the air is not only colder but also much drier.
Germs spread in microscopic droplets of water, sprayed around when someone sneezes. These droplets evaporate slowly in a warm and moist environment but quickly in dry air. The larger a droplet is, the faster it will come down to the ground, the smaller the chance someone else breathes it in and gets infected.
In dry air viruses are in very small droplets that remain airborne almost indefinitely.
At least, that's what the researchers came up with to explain their results.
The Chinese advice to stay in is not specifically meant to create adverse conditions for flu contamination but rather to avoid meeting people with flu at all.