By Jason Gale
April 23 (Bloomberg) -- An urgent probe into an unusual flu outbreak that’s infected seven people in the U.S. was widened after Mexico sought assistance to investigate more than 130 cases of severe respiratory disease that may be related.
Authorities in Mexico asked the Public Health Agency of Canada to help identify the cause of the lung illness linked to 20 deaths, including two in the state of Baja California Norte, which borders California. The Mexican cases include five health- care workers, the Ottawa-based agency said in an e-mail today.
Tests in Mexico found patients were infected with H1N1 and type-B influenza strains and the parainfluenza virus, the agency said. In the U.S., doctors discovered a new strain of H1N1 swine influenza in patients in San Diego County and Imperial County, California, and in San Antonio, the Centers for Disease Control and Prevention in Atlanta said today.
“It will be critical to determine whether or not the strains of H1N1 isolated from patients in Mexico are also swine flu,” Donald Low, an infectious diseases specialist at Toronto’s Mount Sinai Hospital, told the Canadian Press.
Canada’s National Microbiology Lab received 51 specimens from Mexico yesterday and will be testing them for a range of pathogens, the public health agency said.
Thirteen fatal cases of severe respiratory illness were reported in Mexico City, four in San Luis Potosi, a city north of the capital, and another in Oaxaca city in the south. Most cases occurred in southern and central Mexico in previously healthy adults aged 25 to 44 years old.
Fever, Headache
Symptoms include high fever, headache, eye pain, shortness of breath and extreme fatigue with rapid progression of symptoms to severe respiratory distress in about five days, the Canadian agency said. A “high proportion” of cases require mechanical respirators, it said.
In contrast, the four males and three females diagnosed with swine flu in the U.S. have had mild flu-like symptoms. The patients, aged 9 to 54 years, began feeling unwell from March 28 to April 19. All have recovered and only one was hospitalized briefly, according to the CDC.
Preliminary analyses of the virus indicate it contains four different gene components representing both North American swine and avian influenza, human flu and a European/Asian swine flu.
“We have determined that this virus is contagious and is spreading from human to human,” the CDC said in a statement on its Web site. “We have not determined how easily the virus spreads between people.”
Swine influenza is a respiratory disease of pigs caused by type-A influenza that regularly causes outbreaks among the animals, according to the CDC. Swine flu doesn’t normally infect people, though human infections do occur and cases of human-to- human spread of swine flu viruses have been documented.
‘Reassortment’ Risk
Infection in pigs is regarded as especially problematic because of the risk of “reassortment” to produce a new virus, the European Centre for Disease Prevention and Control said in a statement. There is even a risk of a pandemic strain either in pigs or in a person infected with both a human and pig strain, the center said yesterday.
“The infection of humans with a novel influenza A virus infection of animal origins as has happened here is of concern because of the risk, albeit small, that this could represent the appearance of viruses with pandemic potential,” the ECDC said.
Global flu contagions start when a novel influenza type-A virus, to which almost no one has natural immunity, emerges and begins spreading. Experts believe that the so-called 1918 Spanish Flu pandemic, which may have killed as many as 50 million people, began when an avian flu virus jumped to people.
To contact the reporter on this story: Jason Gale in Singapore at j.gale@bloomberg.net
Last Updated: April 24, 2009 00:25 EDT
hat-tip AlaskaDenise
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