ion of virus. Genetic mutations in the virus lead to slightly different version of each card (analogous to the difference between the king of hearts and the king of diamonds). To evade attack by the host or a drug treatment, the virus continually changes the eight cards in its hand. In addition, if any host is simultaneously infected by two different viruses, the viruses can swap genetic cards and create new hands, or combinations of the eight genes in their genome. This is a process known as “reassortment,” and it occurs continually among viruses (see FIGURE 1 for details).
FIGURE 1: Genetic mixing of viruses: The genetic material inside the virus, directs, among other things, the production of proteins found on the outside of the virus shell, shown here as colored shapes on the circular virus coating. If two viruses simultaneously infect the same host (in this case, a pig cell in pink), the viruses’ genetic information may mix, leading to a new strain with characteristics of both original viruses. In this way, genetic material from pig, bird and human viruses has combined to form the 2009 H1N1 strain.
Reassortment can lead to novel combinations of the virus, with the combinations having different rates of infection or clinical symptoms. Since there are many parts of the world where humans have close contact with pigs and birds every day, the viruses can jump from one host species to the next. The various combinations of this novel H1N1 influenza virus are thought to have been introduced into pigs over an 80-year window.
We do know that H1N1 viruses are not spread through food, so eating properly cooked pork (or chicken) is safe. As far as human-to-human transmission, most of this can be prevented by standard measures of frequent handwashing and covering your mouth when coughing or sneezing. Now that summer is here, the CDC has shown that the amount of chlorine used in swimming pools and even tap water is adequate to inactivate other types of flu virus, so spread of the 2009 H1N1 through water is not likely.
Are 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 Organizatio