By Margaret A. Wissman, DVM, DABVP —Avian Practice
You learned about swine flu and influenzas in the August 2009 issue of BIRD TALK magazine. Now learn more about this particular virus.
Let’s do a quick review of what the influenza virus is and what we need to know, then we’ll talk specifically about the swine flu. Influenza viruses are in the family Orthomyxoviridae (Types A, B and C). Influenza A is the only type that is of concern to veterinarians, as this virus has been recovered from a wide range of hosts, including humans, other mammals and birds.
We do need to have a basic understanding of some technical information, including how the viruses are identified. One common identification scheme is based on the variances in the hemagglutinin (H) and neuraminidase (N) proteins found on the surface of the virus. Currently 14 different hemagglutinin proteins and nine different neuraminidase proteins have been detected. Individual sub-types of the influenza A viruses found in birds can be composed of any mixture of one of the hemagglutinins and one of the neuraminidase proteins. The recent outbreak of Avian influenza A in Thailand, Cambodia, China, Indonesia, Japan, South Korea, Laos, Vietnam and Hong Kong is classified as H5N1.
Another identification scheme used has five parameters: the type of virus, host from which the virus was originally recovered, geographic location from which the original isolate was made, reference number and year of isolation. So, "A/duck/Ireland/113/84" (H5N8) is a type-A influenza that was recovered initially from ducks in Ireland in 1984. Interestingly, ducks are probably the largest reservoir of avian influenza, especially the H5N1 serotype.
There are hundreds of subtypes of influenza A viruses that have been isolated from free-ranging birds, domestic poultry, humans, swine and horses, and they are all related. Because this group of viruses is constantly undergoing changes, this results in the frequent appearance of new serotypes to which a population of hosts has no immunity to. This means that the virus keeps changing to stay ahead of the immune systems of susceptible hosts. Such changes are called antigenic shift, and this is why flu epidemics are common year after year.
What You Can Do
How can you remain healthy during this outbreak? Everyone must take everyday actions to stay healthy. Cover your nose and mouth with a tissue when you cough or sneeze. Throw used tissues in the trash immediately after use. Wash your hands often with soap and water, especially after you cough or sneeze to prevent the spread of any infections. Alcohol-based hand sanitizers are also effective and should be used frequently if clean water and soap are not readily available. Avoid touching your eyes, nose or mouth, especially when in a public place, as germs spread easily in this manner. The Center for Disease Control (CDC) recommends that you stay home from work or school if you are ill, and limit your contact with others, to keep from infecting anyone else. Follow the advice from public health officials regarding school closures. Avoid crowds whenever possible.
How It’s Diagnosed
Diagnosis, while challenging, is made by using certain tests, including reverse transcription polymerase chain reaction (PCR) and cell culture of material obtained from sputum or from oropharyngeal or nasopharyngeal swabs. Currently, it is recommended that tests be sent to the state lab or state department of health, and then samples are sent to the CD