A nine-year-old child from south London has become the fifth person in Britain to die after contracting swine flu, the National Health Service said today.

The child, who had serious underlying health problems, is the second person to die in the capital since the flu outbreak spread from Mexico to Britain in April.

A 19-year-old, who was also from south London and had serious pre-existing illnesses, died from the infection last week.

"Once again we would wish to take this opportunity to remind the public that for most people this is a mild illness and that they should start to feel better after a few days without needing to go to their GP or A&E," NHS London said in a statement.

"However, some people may be more susceptible to the virus. If you have flu-like symptoms, it is important that you talk to your doctor if you are pregnant, very young, over 65 or have long-term conditions, such as asthma or diabetes."

The World Health Organization declared on June 11 that the outbreak of the virus was a pandemic. More than 77,000 people have been infected worldwide, including about 7,500 confirmed cases in Britain.

Most people who have caught the infection have suffered mild symptoms, but in a small minority it has proven more severe.

Health Minister Andy Burnham said last week Britain is projecting more than 100,000 new cases a day of the H1N1 flu by the end of August and will change the way it deals with the virus.