Swine Flu Outbreak Caused By New Variant of Old Bug
By John Lauerman and Jason Gale
April 26 (Bloomberg) -- International health officials are wrestling with how to respond to a swine flu from Mexico that’s infecting people, causing a range of illnesses, and even death.
The World Health Organization called the outbreak a “public health emergency of international concern” yesterday, and as many as 81 deaths in Mexico were linked to the virus, normally transmitted among pigs. Eleven cases in California, Kansas and Texas, all of them mild, have been connected as well. At least eight students in New York are being tested for whether they match the Mexico strain, while 10 students in New Zealand are “highly likely” to have swine flu, officials said.
Fears of a lethal pandemic lie in the nature of flu germs, which mutate readily and can become virulent by exchanging genes with related influenza viruses. While the H5N1 bird virus that spread across Asia in the last few years, killing millions of fowl and several hundred people, never gained genes to spread easily among humans, the Mexican swine flu already has, said Malik Peiris, a microbiologist from the University of Hong Kong.
“The concern is that this virus has the ability to transmit from humans to humans because a number of the cases who got infection have had no direct exposure to swine,” said Peiris, who has studied the SARS and avian flu viruses. “That is certainly a cause for concern.”
Health officials said they are trying to determine how the virus gained its ability to infect and spread among humans.
Mexican President Felipe Calderon declared a swine-flu emergency, giving him powers to order quarantines and suspend public events in the nation, where 1,324 patients are hospitalized with flu-like symptoms.
Authorities closed schools until May 6 in Mexico City and the states of Mexico and San Luis Potosi, where infections have been concentrated, and canceled most public and official activities.
The U.S. Centers for Disease Control and Prevention, an Atlanta-based agency, is leading the search for more cases than the 11 it has confirmed as of yesterday.
The latest U.S. tally includes two adults residing at the same address in Dickinson County, Kansas. Neither of the patients was hospitalized, the state’s health department said in a statement on its Web site yesterday. One is still ill and being treated, and one is recovering, it said. One of the patients had recently traveled to Mexico, flying in and out of Wichita, according to the statement.
New Zealand Students
Ten New Zealand high school students who returned from Mexico are “highly likely” to have swine flu, Health Minister Tony Ryall said today in a phone interview.
The students don’t have “severe” symptoms and most already appear to be recovering, Ryall said. The students and their families are being isolated in their homes, and the families are being treated with Roche Holding AG’s Tamiflu, Ryall said.
Japan began screening for fever in travelers returning from Mexico fevers, the country’s health ministry said in a statement yesterday. A British Airways Plc crewmember was hospitalized in north London with suspected swine flu after arriving yesterday on a flight from Mexico City. Tests showed he doesn’t have the bug, Agence France-Presse said, citing a hospital spokesman.
France is investigating two suspected cases of swine flu in travelers recently returned from Mexico, AFP said, citing a senior health official. A spokeswoman for the Health Ministry declined to comment when contacted by Bloomberg News.
Outbreaks in Mexico and the U.S. warrant an urgent assessment of its potential to spark the first influenza pandemic in 41 years, the WHO said yesterday. The Geneva-based United Nations agency held an emergency meeting and found that more evidence is needed to determine whether the level of pandemic alert should be increased, it said.
The WHO’s pandemic threat level, a six-stage measure, is currently at 3. Evidence of increased human-to-human spread of a new virus would move it to level 4, according to the WHO Web site.
Health officials in the U.S. are asking both doctors and patients to be on the lookout for suspicious cases of flu. The lung virus normally causes symptoms such as coughing and sneezing, and can also bring on muscle and joint aches, headaches, and even diarrhea and vomiting, according to the CDC.
At a time when scientists can tailor drugs to match a patient’s genetic profile and people live longer than ever, the flu, first described by Hippocrates 2,400 years ago, still has the power to make millions bed-bound for a week and kill the very young, the elderly and those weakened by chronic disease.
The CDC estimates the germ is linked to more than 30,000 U.S. deaths annually.
In most cases, adults can resist succumbing to flu viruses that are identical or very similar to those they’ve been exposed to before. “New” viruses that the human immune system hasn’t seen earlier are the most dangerous, because they can overwhelm the body’s defenses.
Flu germs are classified by two proteins, one known by the letter H, for hemagglutinin, and the other N, for neuraminidase. The Mexican swine flu is an H1N1 flu, the same subtype that caused the pandemic of 1918. Many less-dangerous descendants of that virus are seasonal H1N1 viruses circulating worldwide today, scientists said.
The dominant form of flu circulating in the U.S. in the most recent flu season was an H1N1, said Frederick Hayden, professor of clinical virology at the University of Virginia Health Sciences Center in Charlottesville. That suggests that people who got this year’s flu vaccine, which gave protection against the H1N1 virus, might also have some protection against the swine flu, he said.
1976 Swine Flu
“We need to take the (blood) of individuals who got last season’s vaccine and see whether there’s any evidence of cross- reactivity for this new strain,” he said in a telephone interview. “We need to do the same thing with patients who have had recent infection with the human H1N1 strain.”
The CDC is conducting studies now that might show whether seasonal vaccination might protect people against swine flu. It’s also possible that people who were vaccinated in the 1976 swine flu outbreak, which many flu experts believed was the beginning of a pandemic at the time, are protected, he said.
Vaccine makers are taking the initial steps toward making shots against swine flu. Baxter International Inc., a maker of both seasonal and pandemic vaccines, has requested samples of the swine virus for laboratory testing, said Christopher Bona, a spokesman for Deerfield, Illinois-based Baxter. GlaxoSmithKline Plc, based in London, has had conversations with WHO’s flu division that’s responsible for distributing flu virus samples to drugmakers, said Deborah Alspach, a spokeswoman.
Other companies that make flu vaccine include Novartis AG, of Basel, Switzerland, and Sanofi-Aventis SA, of Paris.
Roche Holding AG, of Basel, has an ample supply of Tamiflu, which can reduce the symptoms of swine flu. Roche has donated a “Rapid Response Stockpile” of 5 million treatment courses to the WHO that’s on 24-hour stand-by to be sent around the world, said Terence Hurley, a spokesman for the company. No request has been made to deploy the stockpile, he said in an email.
Glaxo also has ample supplies of its inhaled Relenza antiviral, which also appears to be effective against the swine flu in CDC tests, Alspach said.
The virus has already evaded the first line of defense that health officials had hoped to use against a pandemic. International flu experts preparing for a pandemic had planned to contain the initial outbreak of a new, lethal strain of flu. The swine flu virus has already spread so far in Mexico and the U.S. that the containment strategy is out of the question, said Anne Schuchat, interim deputy director for science and public health programs at the Centers for Disease Control and Prevention, the Atlanta-based U.S. agency.
“We don’t think we can contain the spread of this virus,” she said yesterday in a conference call with reporters.
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