- Biotech Basics
- Stem Cells
- Psychiatric Disorders
- 2010 Review
- Synthetic Biology
- Disorders of the Mind
- Genetics of Eye Color
- 2009 H1N1 Flu Outbreak
- Genome-wide Association Studies
- Comparative Genomics
- Copy Number Variation
- The Human Genome Project
- Personalized Medicine
- DNA Microarrays
- DNA Art Contest
- Biotech 101
2009 H1N1 Flu Outbreak
2009 H1N1 Flu Outbreak: separating myth from fact
Note: this edition of Biotech101 represents a departure from our traditional article style. Instead, we’ll be exploring details about the H1N1 virus in a “question and answer” format.
What is H1N1?
H1N1 is an influenza virus. More specifically, it is a RNA virus, which means it uses RNA, rather than DNA, as the genetic material.
The H and N letters represent the type of two different proteins on the surface of all influenza viruses – hemagglutinin (H) and neuraminidase (N). The different subtypes of influenza A are classified on the basis of small changes in the structure of these proteins. The different protein forms are assigned an H number and N number. Changes in these proteins allow the virus to evade the immune system or infect new hosts.
Why is it often called “swine flu”?
Initial studies showed many of the genes in this virus were similar to influenza viruses that normally were found in pigs in North America. More detailed studies have shown this particular virus is much more complex – it also contains two genes from flu viruses that normally are found in European and Asian pigs as well as genes from flu viruses that were originally found in birds (thus called avian flu) and humans.
How can this virus infect humans, if it normally infects pigs?
Pigs are capable of contracting both bird and human viruses – to reproduce, the virus infects host cells and copies its genetic material. There are eight segments of the virus genome and each must be copied and assembled into new viruses. Think of them as a hand of playing cards: survival requires that all eight “cards” be incorporated into the next generation 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.
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