Swine flu outbreaks in Mexico, U.S. raise concern
April 24, 2009
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HELEN BRANSWELL
THE CANADIAN PRESS
Laboratories in Canada and the United States confirmed Friday that an outbreak of unusual illnesses in Mexico is caused by swine flu viruses very similar to those found in eight people in California and Texas.
The finding are further proof that there is person-to-person spread of a new flu virus to which many people may have little or no immunity — key ingredients for the development of a flu pandemic. But international authorities, including those at the World Health Organization, were not ready to say that is what the world is watching.
The WHO signalled it was convening a meeting of experts — likely by teleconference — who will advise Director General Margaret Chan on whether to raise the pandemic alert level from the current phase 3 to 4 or beyond. Phase 6 is a pandemic.
In Canada, officials said while public health authorities have investigated a number of cases of illness in people returning from Mexico, to date there have been no positive findings.
“There’s no confirmed cases in Canada,” said Dr. David Butler-Jones, Canadian’s chief public health officer. “We’re working very closely with the Mexicans and the Americans and continuing to provide technical support.”
The WHO said Friday there have been no cases seen outside of Mexico and the U.S., though they urged countries to be on the lookout.
Canada’s National Microbiology Laboratory in Winnipeg tested a variety of samples sent by Mexican authorities earlier this week because the Mexicans were having problems diagnosing what was behind a respiratory outbreak that was sickening hundreds.
To date 20 deaths have been attributed to the virus in Mexico, 40 other fatalities were being investigated and at least 943 across the country were sick from the suspected flu. In Mexico City, authorities closed schools, museums, libraries and movie theatres Friday to try to limit spread.
In contrast, only one of the American cases was hospitalized and that person had other medical conditions.
The Winnipeg lab found 16 samples containing the unusual influenza A H1N1 virus that American authorities discovered in California and then Texas in the past week.
Butler-Jones said Canada was on the alert after the Americans notified the World Health Organization of the findings on April 17. When Mexico then sought help diagnosing an unusual respiratory illness, he said it was hard not to think there might be a link.
“The spidey senses did go off,” Butler-Jones said in an interview.
The acting head of the U.S. Centers for Disease Control, Dr. Rich Besser, said the CDC’s labs also confirmed seven cases in 14 samples sent from Mexico, and that early analysis of the viruses suggested they are very similar to those responsible for the American cases.
Besser revealed U.S. authorities have raised their confirmed case count to eight, with discovery of an additional infection in a child living in San Diego. The person has since recovered.
Besser said the CDC is hearing from the public that they are concerned, adding: “We are worried as well.”
“Our concern has grown since yesterday in light of what we’ve learned since then,” he said during a news teleconference.
Heightened anxiety was also apparent among WHO officials in Geneva. The organization activated its 24 hour emergency operations centre Friday. Both Canada and the U.S. have activated theirs as well.
It wasn’t clear when the decision would be taken on the pandemic alert level, though experts expect events to move quickly in the coming days.
“We’re very concerned. And this is why we’re running our operations centre 24 hours a day and why the DG (director general) is moving to call the emergency committee.... It all indicates the very high level of our concern,” said Gregory Hartl, a spokesperson for the organization.
The viruses responsible for the cases are made up predominantly of swine flu genes. They are influenza A viruses from the H1N1 subtype.
Though human H1N1 viruses have been circulating for decades, it is not clear how much protection previous infection with them would confer against a swine flu virus and in particular this swine flu virus, which looks unlike any experts have seen before.
Flu viruses from an animal source — whether pigs, birds or other mammals — have the potential to cause pandemics because they are generally so different from human viruses that people have little or no immunity to them.
Widespread illness would be expected to occur if the viruses take off and become a pandemic strain. But the severity of the illness caused depends on the virus, and at present these viruses seem to be causing symptoms similar to regular seasonal flu, said Dr. Allison McGeer, an infectious diseases expert at Toronto’s Mount Sinai Hospital.
“What I’m feeling best about is that it does not seem to be a terrible illness. And if this is going to go, then it’s going to be at least to some degree manageable,” she said, noting that even though Mexico is reporting deaths, there are no reports yet that hospitals there are being overwhelmed.
As would be expected in the early hours of a major disease outbreak, there was a lot of confusion about the scope of the problem and the number of confirmed and suspected cases.
Of the eight cases found in California and Texas, most have no evident ties to one another or to Mexico. None have reported exposures to pigs.
Besser said based on the pattern so far, it seems that there may have been a number of generations of person-to-person spread involved, making the notion of trying to snuff out spread of the virus unlikely. But Hartl said the option of trying to contain the outbreak before it could trigger a pandemic is still on the table at the WHO.
Mexican authorities were reporting three separate events in different parts of the country. The earliest report of an uptick of influenza-like illness dates to March 18, the WHO said in a release posted on its website.
Both the WHO and the CDC are sending staff to Mexico to help authorities there get a better handle on the scope of the problem.
In the U.S., the ages of cases range from children to 54 years. All of those have recovered though one had longstanding health problems and needed hospitalization.
It has been reported that in Mexico the majority of cases are young, previously healthy adults in their mid 20s to mid 40s.
The unusual influenza A H1N1 swine viruses were first reported earlier this week, when the CDC announced it had found two human cases of infection with this never-before-seen virus. Testing shows the virus is vulnerable to Tamiflu and Relenza, the two main drugs used to fight flu.
Dr. Michael Gardam, director of infectious diseases prevention and control at the Ontario Agency for Health Protection and Promotion, said the picture will be clearer in the next few days.
“We’re going to be getting a lot more information over the next week. And it will start to become clearer and clearer who the high risk groups are,” he said, noting Canadian health-care systems and public health officials has been planning for a pandemic for years.
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