FIVE per cent of all flu cases here now involve the H1N1 virus. When the figure hits 10 to 15 per cent, likely within the next one to two weeks, Singapore will shift its approach to tackling the virus into full mitigation mode.

With the authorities having already begun on Monday the transition from containing the virus to concentrating on treating patients at high risk, the Scientific Committee on Influenza A - set up just over three weeks ago - yesterday shared the data from H1N1 cases seen here so far.

For one, as news headlines over the week have reflected, the number of those who have caught the infection within Singapore has been growing rapidly, though there have been no deaths yet.

The good news: While the fear is that the virus may mutate into a more deadly strain, the committee's genome sequencing study shows that while two different H1N1 viruses circulating worldwide are present here, they are almost the same.

Nor is there evidence the Singapore viruses are becoming drug-resistant, said Dr Martin Hibberd of the Genome Institute of Singapore.

So, has the need for concern been exaggerated? Are such stringent precautions really needed, or has Singapore been overreacting?

The worry is far from unwarranted, stressed Tan Tock Seng Hospital's Dr Lim Poh Lian, as Singapore is still in the early days of the outbreak. Just look at Melbourne, where the number of cases multiplied from 10 to 1,000 in just two weeks.

Said the senior consultant of infectious diseases: "Even seasonal influenza has a mortality rate of one in a thousand, and before that person dies, he could end up on a ventilator very ill."

Some experts put the mortality rate of H1N1 at double that - two deaths in every 1,000 patients.

"It's too early to say that everything is going to be fine," said the Health Ministry's director of medical services, Professor K Satku. "As has happened in countries like the United States, when you start having large number of cases, you're bound to encounter some fatalities. In the US with 30,000 cases, they have had more than 100 deaths."

For now, at 5 per cent, the prevalence of H1N1 is still a far cry from the US where some 82 per cent of all flu cases involve that strain.

Half of cases aged 20 or under

Another key source of concern, is that the young have proved more vulnerable to the virus. One in two H1N1 patients in Singapore are aged 20 or below.

Zooming in on the statistics at KK Women's and Children's Hospital (KKH) - where young H1N1 patients are sent - 82 cases have been admitted since June 2, 70 of them children and the rest adult caregivers, said KKH's head of infectious diseases, Associate Professor Chong Chia Yin. The youngest patient was 14 months old.

Most were admitted because they needed to be isolated; only two were sick enough to clinically warrant admission. One had pneumonia, the other patient's asthma took a turn for the worse.

Two pregnant women - one at 19 weeks, the other at 27 weeks - were among the adults admitted and are doing fine. Still, Dr Chong noted, H1N1 patients who are pregnant or asthmatic "may develop complications if they have chronic heart or lung disease".

In this respect, as Singapore moves towards mitigation mode, the community will have a bigger role to play, said Prof Satku.

"Individuals have to exercise good hygiene, coughing and sneezing etiquette. They have to isolate themselves if they come down with the flu. In that way, we can protect other members of the community ... We must be careful that we do not inadvertently expose vulnerable people, especially young children or those with cold morbidities, or pregnant women."

Copyright 2009 MediaCorp Pte Ltd | All Rights Reserved