Antiviral medicines can prevent severe H1N1 flu and should be given to pregnant women, very young children and people with underlying medical problems who fall ill, a World Health Organisation official said on Thursday.

In at-risk groups, in order to prevent progression to severe disease, antivirals need to be administered early, Nikki Shindo of the WHO's global influenza program said.

This also holds for otherwise healthy people who show progressive symptoms, she told a teleconference. Patients with pneumonia also should be treated with antiviral medicines, antibiotics, oxygen, and balanced fluid management.

The WHO has previously said there were only isolated and infrequent cases of resistance to antivirals like osetamivir, marketed by Switzerland's Roche Holding.

Shindo said the pandemic virus had not mutated and that research undertaken since H1N1 emerged earlier this year had shown that antiviral drugs were safe in pregnant women, children under the age of two, and other vulnerable patients.

We are changing the recommendations to make (them) more explicit about early treatment, she said.

Many doctors have been waiting for laboratory confirmation that patients are infected with H1N1, and not something else, before administering antiviral drugs.

Shindo said doctors in places where the virus is known to be circulating should not wait for the laboratory information to start such treatment in high-risk groups.

But she also stressed that healthy people should not take antiviral drugs unless their symptoms worsen quickly, and said that most H1N1 patients would recover without needing any medicines or hospital care.

Hospitals in Afghanistan, Ukraine and Moldova have reported being overwhelmed with patients with H1N1 flu, said Shindo, who suggested early antiviral treatment could help ease this strain.

One way to save lives and lighten the burden on the health care system is to prevent severe disease, she said.

Medicine