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Study in Africa shows majority of pigs with H1N1 virus

Study of Cameroon pigs and the H1N1 virus shows Africa as ground zero for new pandemic, according to UCLA study.

University of California-Los Angeles scientists and an international team of researchers have discovered the first evidence of the H1N1 virus in animals in Africa. In northern Cameroon, researchers tested 11 herds of pigs and found that 89 percent of the sampled pigs had been exposed to the H1N1 virus, commonly known as swine flu.

Because pigs can harbor influenza strains from three different species – pigs, birds and humans – pigs can host influenza viruses that might exchange genes, producing new and dangerous strains.

Results of the study appear in the September 12, 2011, online issue of Veterinary Microbiology.

Pigs run freely in Cameroon, where 89 percent of the pigs in one study tested positive for the H1N1 virus. Image Credit: Kevin Njabo/UCLA Center for Tropical Research

Although H1N1 has been detected in the pigs of 20 countries, there has been no published assessment of the virus in African livestock before this study.

Thomas B. Smith, director of UCLA’s Center for Tropical Research, said:

I was amazed that virtually every pig in this village was exposed. Africa is ground zero for a new pandemic. Many people are in poor health there, and disease can spread very rapidly without authorities knowing about it.

H1N1 triggered a human pandemic in the spring of 2009, infecting people in more than 200 countries. In the U.S., it led to an estimated 60 million illnesses, 270,000 hospitalizations and 12,500 deaths, according to the Centers for Disease Control. The virus, officially known as Influenza A (H1N1), is made up of genetic elements of swine, avian and human influenza viruses.

The pigs in Cameroon, the researchers say, were infected by humans. Lead author Kevin Njabo said:

The pigs were running wild … I was shocked when we found out [they carried] H1N1. Any virus in any part of the world can reach another continent within days by air travel. We need to understand where viruses originate and how they spread so we can destroy a deadly virus before it spreads. We have to be prepared for a pandemic, but so many countries are not well-prepared – not even the United States.

Pigs are unusual – they can be infected with influenza strains that usually infect three different species: pigs, birds and humans. This makes pigs a host where influenza viruses might exchange genes, producing new and dangerous strains. Via Wikipedia

Njabo and his colleagues randomly collected nasal swabs and blood samples from domestic pigs in villages and farms in Cameroon in 2009 and 2010.

Nasal swabs can detect a current infection, and blood samples reveal past exposure to a virus. In a village in northern Cameroon, Njabo found two pigs with active H1N1 infections, and virtually every other pig had evidence of a past infection in its blood.

Njabo said:

The pigs got H1N1 from humans. The fact that pigs in Africa are infected with the H1N1 flu virus illustrates the remarkable interconnectedness of the modern world with respect to diseases. The H1N1 virus that we found in livestock in Cameroon is virtually identical to a virus found in people in San Diego just a year earlier, providing an astonishing example of how quickly the flu can spread all over the globe.

The pig study indicates that H1N1 infections are more common in swine that wander freely in villages than in animals that are confined to farms. (Smith, Njabo and colleagues will hold a workshop in Cameroon next year to tell people how to raise pigs in a way that reduces the risk of disease.)

Viruses in pigs can mix into a much more virulent strain that can spread extremely fast, Smith and Njabo warned. Smith said:

This particular H1N1 strain is ubiquitous. When different strains of influenza are mixed in pigs, such as an avian strain with a human strain, you can get new hybrid strains that may affect humans much more severely and can potentially produce a pandemic that can allow human-to-human infection. This is how a pandemic can arise; we need to be very vigilant.

It would be comforting to believe that the deaths of tens of millions of people, or more, as depicted in the movie “Contagion” is merely science fiction, but something that resembles what is depicted there could happen under a certain set of circumstances.

In the 20th century, the world experienced three influenza pandemics that collectively killed more than 40 million people, Smith and Njabo noted.

In addition to studying pigs, Njabo and colleagues have also collected samples from hundreds of wild birds, ducks and chickens in Cameroon and Egypt. Their colleagues at other institutions are conducting similar studies in China, Bangladesh and elsewhere.

Njabo explained:

There are so many unknowns about the transmission rates of viruses between humans and wild animals. We have to expand screening.

Bottom line: The first evidence of H1N1 in African livestock has been published by UCLA scientists and their team in the September 12, 2011, online issue of Veterinary Microbiology. The study found that 89 percent of pigs tested in northern Cameroon harbored the H1N1 virus.

Read more at UCLA Newsroom

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