Johannesburg — SWINE flu in SA could well outlast the winter season and kill more people than a seasonal flu virus, a virologist said yesterday.

Prof Robert Bragg of the University of the Free State was reacting to a statement from the National Institute for Communicable Diseases yesterday, which confirmed 18 people had died after having contracted the H1N1 virus.

"It is a worrying factor that the mortality rate is picking up so quickly. If the virus were to progress beyond the winter season, it might go above the level of normal seasonal death. So far, indications are that the virus is ... gaining strength, " he said.

Bragg said people had to realise the virus was becoming a potential danger to lives, and that they should be in touch with their medical practitioners.

The institute yesterday confirmed that 5118 people had been infected with swine flu in SA. Nine of the 18 people who had died were pregnant woman -- most of them in the third trimester of pregnancy.

"Pregnancy has been identified as a particular risk factor for severe H1N1 illness in many other countries.... It is critical that infection should receive particular attention in any pregnant woman with influenza-like illness ," the institute said.

In the earlier stages of pregnancy the decision to treat must be made by a doctor based on the clinical condition of the patient.

"In the second and especially the third trimester of pregnancy, urgent treatment should be considered with the appropriate antiviral drugs -- particularly if there is any sign of pneumonia (shortness of breath) and prior to any laboratory testing and results being received", the institute said.

It said other risk factors may include asthma, diabetes, any chronic heart and lung condition and any cause of depressed immunity.