While it is the elderly who are normally at risk in the winter months, unusually it could be the young this year because of swine flu.
In addition there will be other winter viruses such as colds and coughs, vomiting and diarrhoea putting hospitals under a particularly heavy burden.
The threat of swine flu remains uncertain and while it may have plateaued, there is the threat that it will mutate and return in a third wave.
We need to be prepared because this is the first flu pandemic for 40 years and the H1N1 swine flu virus is the first wholly new flu virus seen in a generation.
While in most people it causes only mild illness, it is worse for the under fives, pregnant women and those with chronic illnesses.
That’s why it is worth having the swine flu vaccine if you are offered it.
The decision on whether to have the seasonal flu vaccine is less clear, though it may be worth considering by the elderly because they have lower immunity and less reserve of strength and energy to fight the illness.
But you can protect yourself against other viruses by regular hand washing.
As the weather gets colder viral illnesses will increase, partly because we huddle together for warmth in crowded offices and buses and trains, encouraging viruses to spread.
The best way to cure a cold or flu is let the immune system take over and in most cases it will take four to seven days and will not require any other treatment.