H1N1 flu has killed at least 2,837 people but is not causing more severe illness than previously and the virus has not mutated, the World Health Organization (WHO) said on Friday.

The WHO is carefully monitoring the virus to detect any mutation which might signal that it has become more deadly.

“There is no sense that the virus has mutated or changed in any sense,” WHO spokesman Gregory Hartl told a news briefing. “We are continuing to see increased number of deaths because we are seeing many, many more cases.”

About a quarter of a million cases have been laboratory-confirmed worldwide, but this is far fewer than the true number according to the United Nations agency which has stopped requiring countries to report individual cases.

A WHO weekly statement on the latest strain, commonly known as swine flu, is expected later on Friday. The agency’s previous update of August 28 showed at least 2,185 deaths.

GENEVA (Reuters)