Indirect Transmission: Raccoon -> Poultry -> Humans
Raccoons, also known as procyon lotor, are common animals widely distributed throughout the United States and North America. In a 2009 article in the journal "Avian Diseases," the authors describe the role of wild raccoons in spreading the H3N6 and H4N6 avian influenza viruses to poultry destined for human consumption. While wild birds are well-known reservoirs of avian and other kinds of influenza, domesticated "farm" poultry are intentionally isolated from their wild counterparts to avoid the spread of disease. In this case, according to the authors, laboratory testing ultimately confirmed wild raccoons as a previously unrecognized source of influenza infection in a Pennsylvania poultry farm. To date, according to the Centers for Disease Control and Prevention (CDC), most cases of Avian Influenza (Bird Flu) in humans have been traced to contact with infected poultry, making raccoons an important potential intermediary in the transmission of bird flu to humans.
Indirect Transmission: Raccoon -> Pets -> Humans
According to officials from the U.S. Department of Agriculture, raccoons have semi-aquatic habitats that range up to 20 square miles, which make them a perfect link between wild waterfowl and domestic pets. Infected raccoons spread the virus through feces and secretions from the nasopharynx. Although no cases have been specifically confirmed, the CDC warns that domestic pets such as cats and dogs who sniff or lick infected biomaterial can traffic the infection back to their human owners.
Direct Transmission: Raccoon -> Humans
Theoretically, humans could also acquire the infection through direct contact with raccoons. If a raccoon were to sneeze or hiss in the immediate vicinity of a human, the infection would be transmitted through aerosolized virus particles, just as in many human-to-human transmissions.
In a more likely scenario, however, a human could acquire the disease by touching surfaces contaminated with infected raccoon biomaterial and then touching his or her nose or mouth. The CDC website lists all cases of avian influenza diagnosed in humans since 1996. As of January 2010, there were no proven cases of human-raccoon transmission. However, in more than half of the cases, the source of the infection has not been identified.
References
- Centers for Disease Control
- Avian Diseases; Research Note---Serologic Evidence of Avian Influenza (H4N6) Exposure in a Wild-Caught Raccoon; N.M. Roberts, D.J. Henzler, and L. Clarke; September 2009
- Emerging Infectious Disease; Influenza Infection in Wild Raccoons; J.S. Hall, K.T. Bentler, and G. Landolt; December 2008
