Pregnant women are more prone to get severe or fatal illness when infected with the A/H1N1 flu virus, so they should be considered a priority group for immunization when vaccines are available, the World Health Organization (WHO) said on Friday.

In a statement, the UN agency also "strongly recommends that, in areas where infection with the A/H1N1 virus is widespread, pregnant women, and the clinicians treating them, be alert to symptoms of influenza-like illness."

"Treatment with the antiviral drug oseltamivir should be administered as soon as possible after symptom onset," it said.

"As the benefits of oseltamivir are greatest when administered within 48 hours after symptom onset, clinicians should initiate treatment immediately and not wait for the results of laboratory tests," it added.

According to the Geneva-based agency, worldwide, the majority of the H1N1 patients infected with the pandemic virus continue to experience mild symptoms and recover fully within a week, even in the absence of any medical treatment.

Monitoring of viruses from multiple outbreaks has detected no evidence of change in the ability of the virus to spread or to cause severe illness, it said.

In addition to the enhanced risk documented in pregnant women, groups at increased risk of severe or fatal illness include people with underlying medical conditions, most notably chronic lung disease (including asthma), cardiovascular disease, diabetes, and immunosuppression.

Some preliminary studies suggest that obesity, and especially extreme obesity, may also be a risk factor for more severe disease.

(Xinhua News Agency August 1, 2009)