The H1N1 swine flu has reached epidemic levels in Japan, signaling the early start to what may be a long influenza season this year, and it is also worsening in tropical regions, the World Health Organization said today.
But circulation may have passed its peak in much of the Southern Hemisphere, although it is still midwinter there, WHO said in a regular update on the pandemic.
"In Japan, the level of influenza activity has passed the seasonal epidemic threshold, signaling a very early beginning to the annual influenza season," WHO said in its weekly update on the pandemic.
The first 30,000 doses of pandemic flu vaccine for swine flu are expected to arrive in Ireland next week.
The Health Service Executive (HSE) said yesterday rates of swine flu infection in the community here remained relatively stable.
H1N1 swine flu is now just about everywhere and has been officially a pandemic since June. But, like any infectious disease, it does not spread evenly and can pop up in different communities at different times.
It has continued to spread, at low levels, in the Northern Hemisphere throughout the summer even though influenza rarely spreads in summer. And even where it is flu season, H1N1 is the dominant strain, sickening far more people than seasonal strains of flu.
"In the Southern Hemisphere, most countries (represented by Chile, Argentina, New Zealand, and Australia) appear to have passed their peak of influenza activity," WHO said.
"A few others (represented by South Africa and Bolivia) continue to experience high levels of influenza activity," it added.
More countries are testing the virus to make sure it can be controlled by oseltamivir, the antiviral drug sold by Roche AG under the brand name Tamiflu. So far it does, with a few rare exceptions, WHO said.
Every year, seasonal flu infects between 5 percent and 20 percent of a given population and kills between 250,000 and 500,000 people globally. Because hardly anyone has immunity to the new H1N1 virus, experts believe it will infect far more people that usual, as much as a third or more of the population.
It also disproportionately affects younger people, unlike seasonal flu which mainly burdens the elderly, and thus may cause more severe illness and deaths among young adults and children than seasonal flu does.
Most at risk are pregnant women, people with chronic diseases such as asthma or diabetes and, some studies suggest, perhaps the obese.
Reuters