Avian Flu

For this session, I would post something related to bird flu that has become one of the threatening disease that would affect human globally. Avian flu is caused by influenza type A virus that infects birds and rarely human. Basically, there are 16 H subtypes and 9 N subtypes. H5 and H7 virus subtypes are known to cause highly pathogenic and can cause severe form of disease. The presence of these virus subtypes does not necessarily indicate that these subtypes are highly pathogenic and not all can cause severe form of disease. H5 and H7 subtypes are usually have low pathogenic form when it is first introduced into the poultry but can be transformed into high pathogenic form when they are allowed to circulate for several months. The H5N1 can be divided into two clades or groups (clade 1 and clade 2 viruses) that are circulating among the poultry. Subtypes 2.1, 2.2 and 2.3 are thought to infect human. At the moment, H5N1 flu does not spread to human at high rate. Most of the human cases occurred due to the direct contact between human and sick or dead poultry or dead wild bird, visiting a live poultry market. In 2004 (Thailand), there was a case in which the direct human-to-human transmission was proven due to the prolonged and very closed contact between the ill child and her mother in a hospital. In 2005 (Vietnam), the investigation suggests that the transmission of H5N1 occurred due to the consumption of uncooked duck blood. In 2006 (Indonesia), WHO has reported that 8 people were affected and 7 death was the result. In this case, the source was the   contact between first member and infected poultry. There are many more cases that are not mentioned here.

Treatment:

Basically, there is collaboration between CDC, WHO and National Institute of Health (NIH) in the development of a vaccine for influenza A. Vaccines are not produced for commercial purposes until the new virus has emerged and the disease become pandemic. There are two types of drugs available for influenza: Neuraminidase inhibitors class and M2 inhibitors class. The first class mentioned are still effective and are commercially known as Tamiflu (oseltamivir) and Relenza (zanamivir). The use of the drugs is to reduce the duration and severity of the illness if it is administered early (before 48 hours). The second class mentioned above is not that effective because of the development of resistance. The examples of the drugs are amantadine and rimantadine.

References:

1. World Health Organization, 2005. [online accessed on November 15th  2010]
URL: http://www.who.int/csr/disease/avian_influenza/guidelines/nomenclature/en/index.html

2.   Centers For Disease Control and Prevention. [online accessed on November 15th  2010]
 URL: http://www.cdc.gov/flu/avian/outbreaks/current.htm

3. CBC News, 2008. [online accessed on November 15th  2010]
URL:  http://www.cbc.ca/news/background/avianflu/