WHO chief identifies "warning signs" of severe flu

* H1N1 flu pandemic remains moderate, some patients at risk

* Lethargy, lack of alertness in children is warning

* High fever for more than three days a problem for adults

GENEVA, July 2 (Reuters) - H1N1 influenza is causing mild symptoms that go away without medication in most patients, but care-givers should be alert for warning signs of severe cases, the head of the World Health Organisation said on Thursday.

"The overwhelming majority of patients experience mild symptoms and make a full recovery within a week, often in the absence of any form of medical treatment," WHO Director-General Margaret Chan told a conference in Cancun, Mexico.

"But there are some exceptions that must be the focus of particular concern," she told the meeting, according to the text of her speech distributed by the WHO in Geneva.

Pregnant women and people with underlying health problems are at higher risk from complications from the virus and need to be monitored if they fall ill, Chan said.

Those with normal flu-like symptoms should not seek care in hospitals unless they have certain "warning signs" of severe infection, the former Hong Kong health director stressed.