Experts urge people to get flu vaccine
Flu cases have more than doubled in the past week in England and Wales.
Data from GP surgeries suggests the biggest increase has been in children of school age.
The Department of Health says the figures are in line with what is expected during the winter flu season and says simple hand-washing can help to stop the spread of the virus.
But experts are urging those in high-risk groups, particularly pregnant women, to get vaccinated.
Professor Hugh Pennington, an expert in viruses, said it is very worrying that many people at risk of flu are not being vaccinated.