n graphic documents the spread of H1N1 worldwide as of June 11, 2009. Red circles indicate countries reporting 2009 H1N1 infection. The size of the circle corresponds to the relative number of confirmed cases.
How does the 2009 H1N1 influenza outbreak so far compare to seasonal influenza and previous influenza pandemics?
Seasonal influenza: 3-5 million severe cases each year; 250,000 to 500,000 fatalities annually.
- 1918 pandemic influenza (a member of the H1N1 influenza A family): 500 million cases; 50-100 million fatalities.
- 1957 pandemic influenza (a reassortment of avian influenza A and human influenza A virus): 1-1.5 million fatalities.
- 1968 pandemic influenza (a reassortment of avian influenza A and human influenza A virus): 1 million fatalities.
- 2009 H1N1 influenza (as of June 8): ~29,000 confirmed cases, less than 150 fatalities.
Even though the 2009 H1N1 influenza has relatively low infection and fatality rates, experts are concerned about what the future may hold. Many of the deadly pandemics had multiple waves of illness that spread around the globe, and the 2009 pattern bears similarities to that from 1918. With the 1918 virus, there was a wave of mild illness in the spring in the Northern Hemisphere, followed that fall by the emergence of the extremely deadly form of the virus. Luckily, we have many more infection control measures, diagnostics, and new therapies than in 1918.
Is this the same as the bird flu?
No. In fact public health officials have been expecting that virus, which is an H5N1 influenza primarily circulating in Southeast Asia, to represent the next pandemic. So they were surprised to learn an H1N1 virus apparently with swine origins and starting in Mexico was causing some fatalities and spreading fast – reinforcing the need to expect the unexpected. Scientists are still closely monitoring the avian flu, using new tools like Google Earth mashups (which gathers data from multiple sources) to pinpoint cases.
How is the 2009 H1N1 influenza virus diagnosed?
Most laboratories around the country have “rapid influenza antigen tests,” which take about 30 minutes and detect proteins from the virus’s outer coat only. The molecular method is similar to a pregnancy test, but is used on throat or nose swabs. However, these tests will only identify there is a positive result for a virus of the influenza A family, and will not specify the 2009 H1N1 virus.
More involved tests include utilize a molecular technique known as reverse-transcriptase PCR. Again, the kits in widest use are not specific for the 2009 H1N1 virus, but the US Centers for Disease Control (CDC) has worked quickly to release 2009 H1N1 flu virus sequences on their website, so laboratories could modify this test and single out 2009 H1N1.
One of the best tests was developed by Dr. Jian Han, now a Faculty Investigator at HudsonAlpha and the Chief Scientific Officer for Diatherix, a HudsonAlpha associate company. This test is run on a nose or throat swab, but can detect up to 14 pathogenic organisms from the same sample, including 2009 H1N1.
Will a vaccine be developed for novel H1N1 influenza?
Yes. Even though the traditional flu season is still several months away, vaccine production and distribution takes four to six months, meaning work must begin immediately. The US Department of Health and Human Services (HHS) has already awarded several contracts to pharmaceutical companies to begin producing vaccine against H1N1. As the first step in vaccine production, the CDC and WHO are developing initial stocks of the virus that will be distributed to the pharmaceutical companies by mid July.
By Drs. Chris Gunter and Neil Lamb
HudsonAlpha Institute for Biotechnology
If you want to know more:
- U.S. Centers for Disease Control H1N1 overview: http://www.cdc.gov/h1n1flu/
- World Health Organization updates: http://www.who.int/csr/disease/swineflu/updates/en/index.html
- Using Google Earth mashup to identify H1N1 cases: http://www.nature.com/nature/multimedia/googleearth/