* Developing countries lack antivirals, medical care weak
* Experts fear H1N1 virus more deadly to poor populations
GENEVA, June 12 (Reuters) - Developing countries, where medical care systems are weak and supplies of antivirals insufficient, will be the frontline of the World Health Organisation's battle against pandemic flu.
The new H1N1 virus has caused mainly mild illness among people in rich countries such as Canada and the United States, with most patients recovering without even going to a doctor.
But experts fear it could prove far more deadly to poor populations already weakened by malnutrition, chronic conditions like asthma and diabetes, or low immunity due to HIV/AIDS.
"WHO's primary concern is to strengthen and support health systems in countries with less resources. Health systems need to be able to prevent, detect, treat and mitigate cases of illness associated with the virus," the World Health Organisation said after declaring the first influenza pandemic since 1968 on Thursday.
The United Nations agency was also working to make stocks of antivirals and antibiotics and an eventual pandemic vaccine "more accessible and affordable to developing countries".
"We can say that this is a very contagious virus, it moves very quickly and at times silently, creating asymptomatic cases," WHO Director-General Dr. Margaret Chan said.
The H1N1 strain, commonly known as swine flu, has spread widely after emerging last April in Mexico and the United States. The WHO warned the pandemic could last a year or two.
To date, 29,669 cases of H1N1 have been officially reported in 74 countries, including 145 deaths, most of them in Mexico, but the true number of infections is probably many times more.
The WHO said it was supplying countries with diagnostic kits, medicines and masks and gloves to protect health care workers and minimise the further spread of the new virus.
Fresh stocks of Tamiflu, donated by Swiss drugmaker Roche Holding
, would be distributed to countries needing the antiviral drug, shown to be effective so far against H1N1.
David Heymann, a former senior WHO official now chairing Britain's Health Protection Agency, warned that drug regulatory systems are less efficient in developing countries.
"We need to worry about the development of (drug) resistance if treatment is not done correctly, if inferior doses are used or counterfeit drugs come on the market," he told Reuters.
In Africa, poor communities are vulnerable due to malnutrition, often compounded by respiratory diseases including tuberculosis, according to Heymann, who worked for 13 years in Africa for the U.S. Centers for Disease Control and Prevention.
"This is something that has to be watched very closely. Respiratory disease is already one of the major causes of child mortality in Africa because cooking fires are often in closed houses and the fumes facilitate infections," he said.
"We don't know whether this will be exacerbated by H1N1," Heymann added.
The WHO has urged drugmakers to complete production of seasonal flu vaccine for the northern hemisphere's next winter over the next two weeks, and then switch to production of a pandemic vaccine.
AG said on Friday it expects a vaccine for the H1N1 virus to be available by the autumn after producing the first batch ahead of schedule. The Swiss drugmaker said it would start clinical trials on the vaccine next month. [ID:nLB532879] (For more Reuters stories on swine flu, click on [nFLU]) (For more Reuters swine flu coverage, please click here:
) (For WHO information on swine flu, go to:
) (Editing by Jonathan Lynn)
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