Human Case of Swine Influenza in Texas

November 26, 2008 — 

According to a news article from the University of Minnesota's Center for Infectious Disease Research & Policy (CIDRAP), the U.S. Centers for Disease Control & Prevention (CDC) has been investigating a human case of swine influenza in Texas.

The CDC report indicates the patient, who got sick in mid October, was infected with a swine influenza A/H1N1 virus. The patient reportedly had prior exposure to sick pigs. No additional illness was discovered in the patient's household or close contacts.

Reportedly, the CDC receives approximately one human influenza isolate each year that tests positive for a swine influenza virus. The agency is recommending that clinicians ask patients with unexplained influenza-like illnesses about exposure to animals, including pigs, and visits to petting zoos and county fairs. Human infections with novel influenza A subtypes now are nationally notifiable diseases in the United States.

In December 2007, researchers reported that a new swine flu subtype found in Missouri pigs--H2N3--combined genes from avian and swine flu viruses, could cause experimentally induced infections in mice, and was transmissible in pigs and ferrets. The findings, from a study entitled "Identification of H2N3 influenza A viruses from swine in the United States" which appeared in Proceedings of the National Academy of Sciences (PNAS), bolstered the theory that pigs can serve as a mixing vessel for flu viruses and a possible source for a human pandemic strain.

Most people have some immunity against H3N2 influenza viruses. Although a high proportion of persons occupationally associated with pigs have antibodies to swine H1N1 viruses as well, H1N1 antibody levels are low in the general human population. The emergence in the human population of influenza viruses to which there is little immunity may indicate a possible pandemic threat and should be investigated.

[Ed. Note: Veterinarians are reminded that swine influenza can be a zoonotic disease. If you suspect a case of SIV in pigs you are encouraged to educate the producer about the possibility of human infection and suggest the producer and other farm employees visit their doctor if experiencing any flu-like symptoms. Remind them to inform the doctor that they work around pigs and that influenza has been suspected or diagnosed on their farm.]

Sources:
CIDRAP, November 24, 2008
CDC Swine Influenza Fact Sheet