 the clinical symptoms of the 2009 H1N1 outbreak different from seasonal influenza?
Patients have clinical symptoms that are similar to or even less severe than “regular” seasonal influenza, with one exceptional area: gastrointestional symptoms including nausea, abdominal pain and diarrhea, which are not commonly associated with seasonal flu, have been associated in over 1/3 of the 2009 H1N1 outbreak cases in the US.
Almost ½ of the US cases requiring hospitalization had some underlying condition (pregnancy, lung disease, diabetes, cardiovascular disease etc.), and most or all of the deaths did as well. The death rate for the 2009 H1N1 flu is less than that of other known strains, and nowhere near the mortality in the 1918 pandemic, also caused by an H1N1 virus.
Since a virus causes this type of flu, antibiotics cannot be used to treat it. Antiviral drugs like Tamiflu can still be used to treat this specific 2009 H1N1 strain, but other viral strains have developed resistance to these drugs.
Is the H1N1 outbreak a pandemic?
Many experts say that the flu virus is always teaching us to expect the unexpected. The 2009 H1N1 outbreak has forced scientists and epidemiologists to redefine the very word “pandemic.” Many officials agree with Dr. Michael T. Osterholm of the University of Minnesota: “a pandemic is basically a new or novel agent emerging with worldwide transmission.” Not until June 11th did the World Health Organization (WHO) activate Phase 6 of their “pandemic alert scale,” meaning that they officially recognize the virus is at the pandemic phase; for months before then, the internet was filled with debate over what should be done and when. What we do know for sure is that by early June in the USA, all 50 states and the District of Columbia were reporting cases of novel H1N1 infection. As figure two from the WHO shows, 2009 H1N1 cases had been reported in many countries on almost all continents (these data are also updated each day at http://flutracker.rhizalabs.com/).
FIGURE 2: This World Health Organization 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 