Tue, Jun 16, 2009 - Page 9 News List

It’s a pandemic. But don’t worry ... yet

Although the global ratio of swine flu deaths to cases is low, many hurdles remain before the world can vanquish the A(H1N1) virus — and scientists are not relaxing


Itwas the final surge in numbers that forced the WHO to act. With confirmation last week that swine flu cases had risen above 1,000 in Australia, it was clear the disease was now spreading freely around the world. Thousands of cases had already been reported in the US, Mexico and Chile. Officials at the WHO had no choice. On Thursday, they announced swine flu had achieved pandemic status, the first strain of influenza to reach this mark for 41 years.

It seems an alarming prospect. Are we again set to face a disease that can kill millions as happened with the pandemics of 1918, 1957 and 1968?

WHO Director-General Margaret Chan (陳馮富珍) was confident, however. The disease is only a “moderately severe” risk, she announced. Out of 30,000 cases worldwide, only 145 deaths have been reported. Development of a vaccine — the world’s main anti-flu weapon — is already under way while stockpiles of anti-viral drugs such as Tamiflu are also available, at least for developed nations.

It would be premature to assume complete security, however. Before the world vanquishes swine flu, many hurdles will have to be cleared. In particular, every stage of the development of a swine flu vaccine, our key hope of fighting the disease, could be disrupted, scientists warned last week.

“We must be prepared for something that is more severe than is currently observed,” said Alan Hay, director of the World Influenza Centre, in London. “We cannot be complacent.”

For a start, swine flu vaccine production is still at a very early stage. Indeed, the artificial strain that will form the core of a vaccine has only just been created, with researchers in Britain, Australia and the US having produced almost identical versions. These have only just been passed to pharmaceutical firms to see if they can quickly produce the vaccine on a mass scale.

The British version of the vaccine strain — known as RG121 — was created recently. Like its US and Australian counterparts, it is made of bits of several flu viruses but specifically stimulates immunity against swine flu. Unlike swine flu, however, it can be grown easily in hens’ eggs. Eggs are used throughout the drugs industry as incubators in which viruses — the basic components of vaccines — are grown.

“Hens’ eggs remain the bulwark for vaccine production,” said Peter Dunnill, of the Centre for Biochemical Engineering at University College London.

James Robertson, leader of the team that created the RG121 strain, said:

“It is a pretty ponderous business, however. Each egg has to be looked after carefully and you have to beware lest infections kill them off. Different strains behave differently in eggs and produce varying amounts of virus particles. In the case of our swine flu vaccine strain, we simply do not know yet how much virus you will get from each egg.”

At present, pharmaceutical companies’ estimates of the amounts of virus particles they will get from their eggs are optimistic. Many scientists warn this could be a mistake. Companies might find they get less than a third or a quarter as many viral particles as they hoped for, a reduction that would, in turn, limit the number of vaccine doses available to the public.

Once viruses are extracted from eggs they are broken into pieces including bits of their protein coats. These are important because they stimulate immune responses in humans and can be used to make a vaccine.

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