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Flu Alarm that Fell Flat

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Governments in North America ignored warnings that a swine flu strain was circulating in pig farms.

Canadian paediatrician Joan Robinson’s long-planned holiday to Mexico wouldn’t have been jeopardised and the world may not have been teetering on the brink of a pandemic had authorities acted on her words of caution.

Robinson’s late-June vacation destination is at the centre of a potentially pandemic flu outbreak, which has now spread to 14 other countries in five continents, apart from reportedly killing 160 people since mid-April. Her government, like many others, has issued a travel advisory to avoid non-essential travel to Mexico for a while.

Ironically, Robinson, professor of paediatric infectious diseases at the University of Alberta, Canada, had warned as early as February 2008 that a swine flu strain capable of human-to-human transmission is circulating in North America, particularly in some Canadian pig farms.

No one knows whether it is the same flu strain that’s wreaking havoc now as flu viruses mutate notoriously fast. But had the authorities listened to her, the world wouldn’t have been caught by surprise.

Robinson got a whiff of the trouble brewing when a seven-month-old baby living on a community pig farm was diagnosed with a mild swine flu attack in 2006. Subsequently, her team screened 90 people, who lived on the farm, to find 54 of them positive to the strain. Her paper, in early 2008, called for monitoring pig farm workers in Canada and other countries as part of their national influenza pandemic preparedness plans.

“Countries did not take up any surveillance of swine workers, probably because the number of human swine flu symptomatic cases until 2009 was so small that experts did not think this was an important part of pandemic planning,” she told KnowHow. Early recognition of swine strains becoming virulent is key to infection control as well as vaccine development, she said.

Robinson wasn’t alone in waving the red flag. Gregory Gray, director of the Center for Emerging Infectious Diseases at the University of Iowa College of Public Health, reported in 2006 that some pig farmers and meat processing workers they studied had elevated levels of antibodies against swine flu in their blood — an indicator that they were exposed to the flu virus. More importantly, a team of researchers from St. Jude Children’s Research Hospital in Memphis picked up signals as early as 1998 that flu viruses in pigs were swapping their genetic material, triggering the possibility of newer — maybe more lethal — strains being in circulation.

Thanks to the H5N1 avian flu outbreaks reported in different parts of the world since 2003, including India, the world is better prepared to deal with the emerging crisis. In less than a week of the outbreak being confirmed, the World Health Organization warned that a pandemic is imminent. “It is because of the concerns with the H5N1 virus that we have been able to pick up this outbreak relatively early, and we are much better prepared because of that,” said Michael Osterholm, who heads the Center for Infectious Disease Research and Policy at the University of Minnesota.

International public health experts have enough reasons to be alarmed.

For one, the influenza virus is very unpredictable. A flu strain may be harmless, but a slight change in its genetic composition can turn it into an extremely virulent variety. “The flu virus constantly surprises us,” said Nancy Cox who heads the flu division at the Center for Disease Control and Prevention (CDC) at Atlanta. The source of this surprise — not really a pleasant one though — is the ability flu viruses have to swap their genetic material when two or more of them co-habit. “Analysis of the early isolates suggests that the genetic make up of this new virus is a mixture of the avian, swine and human viral genomes. It is too early to tell how this virus evolved,” said Ram Sasisekharan, professor of biological engineering at Massachusetts Institute of Technology, US.

Then, the fact that the virus originated from pigs was the biggest worry for public health authorities. Pigs have been the ideal mixing vessel for flu viruses afflicting different species: humans, birds and pigs. While it is very rare for other species to accommodate more than one flu strain at any point in time, pigs do that happily, that too without being sick.

Further, the 1918 Spanish flu which killed anything between 50 million and 100 million across the globe too was of swine origin. The similarities, however, seem to end there. Though they are both H1N1 viruses, the novel swine flu does not appear to share any of the genetic markers of the virulence that 1918 pandemic flu virus possessed, according to a CDC statement.

But, there is one thing that makes virologists happy. Genetic analysis of the strains isolated from affected countries — Mexico, the US, New Zealand, Canada, the Netherlands and Germany — indicates that the strain has so far stayed steady, and hasn’t mutated. All genes of these strains have 99 per cent to 100 per cent similarity. This makes producing a vaccine easier, said Cox.

If that is true, the scientists may have to find why the same strain is behaving differently in two different populations. While the number of deaths in Mexico is frightening, there hasn’t been any serious case outside Mexico. While 159 people reportedly died in Mexico (but of these only sixteen are laboratory-confirmed swine flu deaths), there was only one death outside: in the US.

What, however, is puzzling is that the 159 deaths have come from some 2,500 cases reported in Mexico, pointing to a very high fatality rate (the ratio between number of cases and deaths). The Mexican government has stopped reporting suspected cases and deaths since April 30, 2009.

Some of the questions scientists already asking are: Is this because a huge number of Mexicans have been infected? Is that because many of the deaths in Mexico are due to other causes, since only a minority of the people who died were actually tested for swine flu? Is that because Hispanic people have a different response to this virus than white people do? Is that because Mexicans were more likely to be infected by a household member and most others were infected by more casual contact, and so got a smaller dose of the virus? How capable is this virus of efficiently spreading from person to person multiple times?

“Until we have answers to some of these questions, we do not know if the current outbreak will be over shortly (the 1976 US swine flu outbreak lasted 21 days) or will ultimately prove to be a pandemic,” said Robinson.

According to Wendy Barclay, a flu virologist at the Imperial College in London, the outbreak in Mexico may not have such a high case fatality rate. “We don’t know how many people may have been infected but didn’t get very ill,” he says. Every normal pandemic has a case fatality rate of 1 to 2 per cent. “This is the type of figure that governments should have planned for in any pandemic,” Barclay told KnowHow. “But anything beyond 5 per cent could be really bad.”

Sources: The Telegraph (Kolkata, India)

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