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MEXICO's MYSTERY: Why Is Swine Flu Deadlier There?

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Bianca
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« on: April 29, 2009, 07:12:26 am »








                                  Mexico's Mystery: Why Is Swine Flu Deadlier There?
           





YAHOO NEWS
Bryan Walsh
– Tue Apr 28, 2009

The swine flu virus continued its gradual global march on Tuesday, prompting countries to strengthen efforts to stem its spread, while President Barack Obama asked Congress for $1.5 billion in supplementary spending to prepare for a possible swine flu pandemic and installed the newly confirmed Secretary of Health and Human Services, Kathleen Sebelius, to help lead the fight against the disease. In the U.S., the caseload rose to 67 across five states - 45 of them in New York City, where health officials are investigating two new possible outbreaks at city schools - with more virus samples awaiting laboratory confirmation. New Zealand and Israel also confirmed its first cases, while Canada, the U.K. and Spain saw small upticks in their swine flu caseloads.


Several countries tightened border controls and discouraged travel to affected areas - Cuba suspended all flights to and from Mexico - but the World Health Organization kept the pandemic alert level at phase 4, still two phases below a full pandemic. Outside Mexico, the apparent epicenter of the A/H1N1 virus, there have been no deaths confirmed from the flu and relatively few hospitalizations, and health officials continued to preach the need for a calm response. "What we see in the United States, or have been seeing so far, has been milder," said Richard Besser, the acting director for the Centers for Disease Control. (See pictures of the swine flu in Mexico.)


But Mexico seems to be experiencing a very different - and much scarier - outbreak than the rest of the world. More than 2,000 suspected swine flu cases have now been reported in several Mexican states, with more than 150 deaths. Those numbers are still preliminary and are expected to rise as blood samples from Mexican patients continue to be tested for the A/H1N1 swine flu virus. Lack of laboratory capacity to run the time-consuming blood tests has so far held up the confirmation of cases there.


On Tuesday the government of Mexico City ordered gyms, discos, theaters and all sit-down restaurants (excluding those that serve only take-out) closed until at least May 6, in an effort to limit public gatherings and the spread of the virus. As epidemiologists swarm the country in an effort to trace its spread, the big question remains: Why is the disease seemingly so much more deadly in Mexico than anywhere else? "This will be the object of a great deal of research and attention," said Keiji Fukuda, the World Health Organization's (WHO) interim director-general for health, safety and environment. "But we can't say why there seems to be a difference." (See the 5 things you need to know about swine flu.)


The WHO will convene an expert panel on April 29, which will attempt to answer that question, but one way to begin is to look at where the virus originated. Epidemiologists appear to be honing in on a possible ground zero in the Mexican Gulf Coast state of Veracruz, in a town called Perote, which is home to a large pig farm owned by the U.S. company Smithfield Foods. Flu-like cases began popping up there in early April, before the first confirmed case in Mexico on April 13.


But the truth is that even though the virus is referred to as swine flu, researchers do not yet know for sure that the A/H1N1 virus actually originated in pigs. There's been no evidence yet of pigs getting sick, in either Mexico or in the U.S. (Despite several countries' bans on pork imports, it's important to remember that the disease cannot be contracted by eating pork.) The original reservoir for flu viruses is actually wild birds, which can spread infection to domestic birds and people - as we saw with the H5N1 avian flu in Asia - and to pigs. Pigs make particularly good biological mixing bowls, since they can be infected by bird, swine and human flu viruses and provide a hospitable environment for the viruses to swap genes and create entirely new strains in a process called reassortment. That is what may have happened with the A/H1N1 swine flu virus, which contains genes from bird, pig and human flu viruses. "When you get a large concentration of pig farms, people, wild bird and poultry, these things do happen," says Peter Daszak, the president of the Wildlife Trust and an expert on emerging diseases.


In recent years, since the ongoing H5N1 bird flu virus first surfaced, health officials have focused mostly on Asia as the breeding ground for the world's next pandemic flu virus. But Daszak points out that Mexico, where people, pigs and poultry can exist in close proximity, is an overlooked hotspot for new viruses. Given the booming global livestock trade - more than 1.5 billion live animals have been shipped to the U.S. from all over the world in the past decade - it's possible that the A/H1N1 virus originated in an Asian bird that was exported to Mexico, where it may have reassorted in a pig before infecting people. Far more investigation is still needed, but it's clear that while U.S. officials were looking for flu exports from Asia, they should have also improved surveillance in their southern neighbor. "I think it might have been possible to prevent it," says Daszak. "We should be paying more attention to our own backyard."


Now that the swine flu virus seems well established in human beings, containment is no longer an option. The public health response must be to slow the spread, which means getting a better handle on the virus. While the difference in severity in cases between Mexico and the U.S. would suggest that there are different viruses affecting the two countries, researchers have genetically sequenced swine flu viruses from both Mexican and American victims, and "we see no difference in the viruses infecting sick people and less sick people," said Fukuda. Even if there were genetic differences, it wouldn't necessarily mean much - scientists still don't know exactly which genes do what on flu viruses.


The Mexican deaths may also be attributable to some underlying co-infection or health problem that is simply not present in the U.S. cases - but that will require more investigation to uncover.


It's possible also that A/H1N1 began life in Mexico especially virulent - that country has apparently been grappling with the virus for weeks longer than the U.S. - and evolved to become less dangerous by the time it crossed the border. That would not be an unusual evolutionary device, since viruses that are too deadly cannot survive if they kill off their host before they get the chance to spread. "It's fairly common in epidemics to see a tradeoff between the ability to cause severe death and transmissibility," says Steven Kleiboeker, a virologist and the chief scientific officer for ViraCor Laboratories. The A/H1N1 virus may be attenuating itself as it spreads from person to person, becoming easier to catch but less dangerous. (Read: "CDC Readies Swine Flu Vaccine.")


The WHO, however, says that so far the virus appears to have stayed relatively stable during the chains of transmission, so it may not be mutating much. Still, the virus's current relatively weak state does not guarantee that it won't return later much more virulent - exactly what happened in the 1918 flu pandemic, which killed at least 50 million people worldwide. As the flu season comes to an end in the Northern Hemisphere, it may lead to a natural petering out of new swine flu cases in the U.S. But the strain may continue to circulate aggressively in the Southern Hemisphere, which is just now entering its flu season, then return to the north next winter.


Any conclusions now will be premature, because we still don't know what we're looking at. Experts predict we'll eventually begin to see fewer new cases in Mexico, as lab results separate real swine flu infections from normal respiratory disease. Officials also anticipate more cases in the U.S., as well as fatalities, as the nationwide investigation deepens. "We expect to see more cases and we expect to report on them," says Besser. "As this moves forward, I fully expect that we will see deaths from this infection." As Besser himself has pointed out, swine flu is going to be a marathon, not a sprint - and we've only just gotten started.
« Last Edit: April 29, 2009, 07:31:42 am by Bianca » Report Spam   Logged

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Bianca
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« Reply #1 on: April 29, 2009, 03:08:55 pm »











                                                Science takes aim at the swine flu







YAHOO NEWS
Peter N. Spotts
– Mon Apr 27, 2009


Governments confronting a new strain of swine flu from Mexico have an unprecedented set of scientific tools to help them. The result is steady improvement in dealing with outbreaks like the current one.

Yet experts say a lack of clear communication in Mexico about the status of the outbreak and what people could do to protect themselves was perhaps a major factor in how the strain spread throughout the country and the world.

In the US, public-health officials said Monday they have identified 40 cases, with one person hospitalized. But "things are working well, from what I can see," says Peter Hotez, who heads the department of microbiology, immunology, and tropical medicine at George Washington University in Washington.

The faster speed of communications helps: Word of a problem gets out much more quickly than it did 20 years ago. But science, too, has improved its ability to identify an illness's origins, assess its susceptibility to existing vaccines, and model the trajectory the outbreak could take, experts say.

Researchers say they have increased their capacity to recognize and understand the nature of the biological agents involved. Even six years ago in the case of SARS, scientists needed only a relatively short time – six weeks – to characterize the agent involved, says Myron Cohen, director of the University of North Carolina's Institute of Global Health and Infectious Diseases. And SARS was something no one had seen before. Previously, that process might have taken years.

As for the outbreak of illness in Mexico: "Look how quickly we understood that it was an influenza agent, which in many ways is reassuring," Dr. Cohen says. "The ability to gain information on the agent and its pedigree is really quite remarkable."

Moreover, there are more labs and equipment that can do the work. When US labs reportedly required extra paperwork to analyze samples of the flu agent, public-health officials in Mexico simply sent the samples to labs in Canada. In California, the first diagnosed cases of swine flu from the Mexican outbreak were uncovered by researchers developing new test kits physicians could use in their offices, according to Richard Besser, acting director of the Centers for Disease Control and Prevention (CDC) in Atlanta during a briefing Monday.

In the US, officials already have started moving vaccines out of stockpiles and to healthcare providers. At this point, the CDC has released about 25 percent of that stockpile.

If the outbreak becomes more serious than it currently appears, Dr. Besser says, "doctors will have what they need."

For all the technological progress, however, more needs to be done, say some specialists.

Though the technology now exists to respond quickly – reducing the time it takes to design and evaluate a new or modified vaccine, it will take money to put the technologies in place, says Dr. Hotez.

Early detection remains an issue in some parts of the world, as well. The outbreak's origins in Mexico, for example, are largely a mystery. "We do not know how long this virus has been circulating and capable of human-to-human transmission," says Ted Cohen, an assistant professor of medicine at Brigham and Women's Hospital in Boston. "Certainly, the wide geographic distribution of cases indicates that our detection systems were not able to contain the virus where it initially emerged."

"This delay undoubtedly has limited our ability to respond to this potential crisis with travel restrictions or others methods that might have potentially prevented the long-distance spread of this pathogen," he adds.

Lessons from the past also show clearly that keeping people well-informed and apprised of developments is the best thing to do. "But it's not a lesson all governments have learned," says David Ozonoff, a communicable-disease specialist at Boston University.

He points to Mexico, which, he says, has been "authoritarian on one hand and not very informative on the other" with the public. The situation is compounded by a general lack of public trust in anything government officials say, he adds.

The United Nations' World Health Organization (WHO) generally has done a good job responding to the outbreak, Dr. Ozonoff says, but has underplayed the outbreak's severity. During the weekend, it hovered at 3 on the agency's 1-to-6 scale – even when it was clear by the scale's definitions that the outbreak was a 4 or 5, he says. "There are consequences" to higher ratings, he says, which include trade and travel restrictions. Today, the WHO raised the severity of the outbreak to Level 4.
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