Image caption Much of the trade in wildlife meat, or bushmeat, has its origin in Africa

Scientists have documented potentially dangerous viruses entering the US through illegally imported wildlife products.

Testing of meats confiscated at American airports has revealed the presence of several pathogens that could pose a risk to human health.

Retroviruses and herpesviruses were identified, some of them isolated from remains of endangered monkey species.

The research study is reported in the journal PLoS One.

Its authors say better surveillance measures are needed to ensure this trade does not result in the emergence of new disease outbreaks in humans.

"Although the findings to date are from a small pilot study, they remind us of the potential public health risk posed by illegal importation of wildlife products - a risk we hope to better characterize through expanded surveillance at ports of entry around the country," said Dr Kristine Smith, from EcoHealth Alliance, who led the investigation team.

Scientists estimate that some 75% of emerging infectious diseases affecting people have come from contact with wildlife.

Some of this is the result of animals biting humans, but the handling and consumption of infected meats is also considered a significant route of transmission.

Classic examples of infections that have jumped across the species include HIV/Aids, which is thought to have originated in primates, and Sars, an infection that caused global concern in 2003.

Follow-up work traced its beginnings to Chinese restaurant workers butchering the cat-like Asian palm civet.

The PLoS One study is a first attempt to screen for potentially hazardous pathogens in confiscated meat products entering the US.

The scientists examined animal remains passing through five international airports, including John F Kennedy in New York - one of the busiest hubs in the world.

The smuggled meats - some found in postal packages, some discovered inside suitcases - were tested first to make a species identification.

This showed up several non-human primates, included baboon and chimpanzee, but also rodents.

The raw, smoked and dried meats were then tested for a number of viruses known to be capable of infecting humans.

Among the pathogens identified were a zoonotic retrovirus, simian foamy viruses, and several nonhuman primate herpesviruses.

No-one really knows the scale of the illegal trade in wildlife meat, or bushmeat as it is often called, but a 2010 study estimated that five tonnes of the material per week was being smuggled in personal baggage through Roissy-Charles de Gaulle airport in Paris, France.

And in addition to the meat products, there is a big trade in live wild animals. Much of this is perfectly legal and supplies the pet industry. Nonetheless, these animals also require improved pathogen surveillance, say the researchers.

"Exotic wildlife pets and bushmeat are Trojan horses that threaten humankind at sites where they are collected in the developing world as well as the US. Our study underscores the importance of surveillance at ports, but we must also encourage efforts to reduce demand for products that drive the wildlife trade," said Ian Lipkin of Columbia University's Mailman School of Public Health.

One key aspect of concern highlighted by the team was the identification in the samples of some endangered species, including the Guinea baboon and the sooty mangabey, an Old World monkey.

Marcus Rowcliffe, from the Institute of Zoology in London, UK, and who was not connected with the research, commented: "The extent to which an intercontinental luxury meat market may be developing is of major concern, because if that is happening it could have very worrying impacts on wild populations.

"This whole area is marked by a lot of unknowns which is why we need more studies like this."