Five additional cases of swine influenza reported

Five additional cases of a unique type of swine influenza A (H1N1) were identified today at the CDC, bringing the total to seven, and it is likely that total will rise, health officials said. Five of the cases occurred in southern California; another two cases occurred in San Antonio.

Anne Schuchat, MD, of the National Center for Immunization and Respiratory Diseases at the CDC, said none of the seven people had direct contact with pigs, making human-to-human transmission a likely source of infection.

The first two cases were reported Tuesday. Schuchat said CDC officials stepped up surveillance for this type of influenza in Texas because one of the initial cases – a 10-year-old boy – travelled to Dallas from California. However, no cases of this particular strain of swine influenza have been found in Dallas and the San Antonio cases appear unrelated.

Schuchat said three girls and four males, aged 9 to 54 years, have been affected. All patients presented with respiratory symptoms and all have since recovered from their illnesses.

CDC investigators are learning more about the genetic makeup of the illness. The researchers said that this type of influenza contains genetic material found in avian, human and swine influenza viruses found locally and in Europe and Asia. The virus is resistant to amantadine and rimantadine and susceptible to oseltamavir and zanamivir.

Since all cases occurred along the Mexican-U.S. border, health officials are working with the Mexican government to identify strains there as well.

Schuchat said that researchers are looking at this strain as a potential vaccine seed strain.

CDC officials emphasized that the virus cannot be contracted by eating pork or pork products. They emphasized hand hygiene as a good way to reduce spread of all respiratory viruses.

Physicians are being asked to “consider animal as well as seasonal influenza virus infections in their differential diagnosis of patients who have febrile respiratory illness and who 1) live in San Diego and Imperial counties or 2) traveled to these counties or were in contact with ill people from these counties in the seven days preceding their illness onset, or 3) had recent exposure to pigs.” They added that physicians who suspect this virus should get a specimen and contact state health officials. – by Colleen Zacharyczuk