Avian influenza outbreaks create concern about human infection Mayo Clinic researchers warn

The occurrence of avian influenza in humans is a reminder of the vulnerability of people to an emerging pandemic, Mayo Clinic researchers warn in the current issue of Mayo Clinic Proceedings.

Mayo Clinic researchers review the latest outbreak of highly pathogenic avian influenza (H5N1 strain) that occurred recently among poultry in eight Asian countries. The researchers review current knowledge about avian influenza and how to manage this emerging disease.

ÒAn immediate priority is to halt further spread of epidemics in poultry populations that would reduce the opportunities for human exposure to the virus,Ó says Larry Baddour, M.D., of the Mayo Clinic Division of Infectious Diseases and Internal Medicine and the lead author of the article. ÒClinicians should be cognizant of human influenza H5N1 infection among patients with the appropriate epidemiological exposure, so that patients can be identified quickly and managed appropriately and health care workers can be protected.

Dr. Baddour also notes that a vaccine against this virus needs to be developed.

Since mid-December 2003, Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand and Vietnam have reported outbreaks of the avian influenza strain H5N1. Vietnam and Thailand have reported influenza H5N1 infection in humans with 32 laboratory-confirmed cases and 22 deaths, a mortality rate of nearly 70 percent. More than 100 million domestic poultry have been killed to halt the epidemic and prevent transmission to humans.

Two of the three criteria that characterized the influenza pandemic of 1918-1919 have already been fulfilled in the current epidemic of avian influenza: the ability of the virus to infect humans resulting in high mortality, and a global immunologically naive human population. The third criterion, efficient human-to-human transmission, has not been observed.

Researchers are concerned because influenza viruses mutate frequently, potentially allowing them to change the host receptor specificity from avian to human.

The authors of the Mayo Clinic Proceedings report offer some general precautions for preventing the spread of the virus, such as performing thorough and frequent hand washing using soap and water or alcohol-based hand rubs. The virus can be killed with heat (132 degrees Fahrenheit for three hours, 140 degrees for 30 minutes or 158 degrees for one minute) or common disinfectants such as alcohol or bleach for inanimate objects contaminated by the virus.

All hospitalized patients diagnosed as having or being evaluated for avian influenza should be isolated for 14 days after onset of symptoms, until an alternative diagnosis is established, or until diagnostic test results indicate that the patient is not infected with influenza A. The same time frame should be used for outpatients.