Dr Margaret Chan says avian flu is more of a problem than swine flu
The head of the World Health Organisation (WHO) has warned the global swine flu pandemic is not yet over and the virus could still mutate.
Dr Margaret Chan said it was important to "guard against complacency" despite signs the disease had peaked in North America and parts of Europe.
She said the virus was still active in countries including India and Egypt.
More than 11,500 people are believed to have died in more than 200 countries and territories because of swine flu.
However Dr Chan said it would take at least two years before a true death toll could be established.
The WHO's director general said the US, Canada and the UK were among those countries where the worst of the swine flu outbreak had appeared to have passed.
But she added: "It is too premature and too early for us to say we have come to an end of the pandemic influenza worldwide."
She said experts needed to continue monitoring the pandemic for another six to 12 months as it could mutate into a more dangerous strain.
"We will watch this virus with eagle's eyes," she said.
SWINE FLU SYMPTOMS
1. High temperature, tiredness and lowered immunity
2. Headache, runny nose and sneezing
3. Sore throat
4. Shortness of breath
5. Loss of appetite, vomiting and diarrhoea
6. Aching muscles, limb and joint pain
Dr Chan said it was fortunate the pandemic had been milder than expected.
"The fact that the long overdue influenza pandemic is so moderate in its impact is probably the best health news in a decade," she said.
Millions of people are believed to have recovered after contracting the virus and displaying few symptoms.
She said the demand for swine flu vaccinations in some European countries had been lower than expected and WHO was investigating whether superfluous vaccines could be sent to developing countries.
Dr Chan said drug makers and countries promised to donate nearly 190 million vaccine doses to WHO, with the first doses of the donated vaccines to be distributed in Azerbaijan, Mongolia and Afghanistan next month.
However she admitted she had not yet had a vaccine but said she would have it soon.
She said that although countries are now better prepared to cope with a global disease outbreak, people still had to be aware of the dangers of bird flu (H5N1).
She said this was more toxic and deadly than swine flu and that many countries remained ill-prepared for mass outbreaks of this virus.
"The world is not ready for a pandemic to be caused by H5N1," she said.