Senior author Thomas B. Smith, director of UCLA's Center for Tropical Research, said H1N1 triggered a human pandemic in the spring of 2009, infecting people in more than 200 countries and in the United States, it led to an estimated 60 million illnesses, 270,000 hospitalizations and 12,500 deaths.
The virus, known scientifically as Influenza A (H1N1), is made up of genetic elements of swine, avian and human influenza viruses. The pigs in Cameroon were infected by humans, Smith said.
"The pigs were running wild in that area," lead author Kevin Njabo, associate director of the Center for Tropical Research, said in a statement.
"I was shocked when we found out it was H1N1. Any virus in any part of the world can reach another continent within days by air travel. We have to be prepared for a pandemic, but so many countries are not well-prepared -- not even the United States."
This particular H1N1 strain is ubiquitous, Smith said.
"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," Smith said.
The findings were published in Veterinary Microbiology.