Swine flu has been declared a global pandemic, at the highest level of the World Health Organisation's alert scale.
The World Health Organisation on Thursday raised its pandemic flu alert to phase six on a six-point scale, indicating the first influenza pandemic since 1968 is underway.
The WHO reiterated its advice to its 193 member countries not to close borders or impose travel restrictions to halt the movement of people, goods and services.
The move to the organisation's highest alert level reflects the fact that the new H1N1 flu, a mixture of swine, bird and human viruses, is spreading geographically, but does not indicate how virulent it is.
Director-General Dr Margaret Chan said the global assessment is that there is a "moderate pandemic."
A unanimous experts' decision was based on an overall assessment in the eight most heavily hit countries - Australia, Britain, Canada, Chile, Japan, Mexico, Spain and the United States - that the virus is spreading in a sustained way in communities, Dr Chan said.
"Moving to pandemic phase six level does not imply we will see an increase in the number of deaths or very severe cases", she said.
On Thursday the number of confirmed cases of the virus worldwide was at least 28,799 in 74 countries.