Ecology of the Flu Virus

The flu virus even though it consists solely of scraps of RNA functions as a parasite on its host at the cellular level. As a parasite, it requires fresh cells to infect and reproduce on a constant basis because the cell can only survive a short while outside a host organism. It only remains infectious for about a week at body temperature and up to a month at 32 degrees Fahrenheit. As a parasite, it is in the virus’ best interest to not kill the entire organism so it can continue to reproduce and infect others and spread. However, the host organism develops antibodies after being infected. As a result the same host cannot be infected multiple times by the exact same strain of the flu virus. This causes the flu virus and host organism to have an enormously accelerated parasitic relationship where each must mutate and adapt after each infection.

The aforementioned relationship between host and the flu virus means the virus is most devastating in confined areas where the rate of transmission is high. The flu also requires a minimum pollution density where there are enough hosts to perpetuate the virus. Because of the nature of the disease many viruses including the flu virus are nicknamed “crowd or herd diseases.” Additionally, the flu has seasonal epidemics because each host develops immunity to subsequent infections from previous strains that it has contracted. There are two flu seasons annually, during the winter of the northern and southern hemispheres. While the exact reasons for the season being in the winter are unknown, organizations like CDC can track the flu as its season progresses around the world. By the tracking the flu virus, we can predict next season variant. As the virus migrates, it gradually mutates to become infections the previous populations that it has infected. This small mutation is essential the parasitic relationship because it makes the virus unrecognizable by any previous hosts antibodies and thus the need for a new flu vaccine each year.

While flu vaccines have come a long way, there is little hope for a vaccine for all flu viruses. Vaccines function by exposing the body to non infectious virus’s to create antibodies. The flu mutates too quickly and is an ecologically resourceful virus. Any organism can increase its chances of survival by having multiple sources of resources. In the case of the flu, it has multiple species as hosts. Birds are thought to be the source of the flu virus, and can carry the virus to all parts of the world. Through the virus’s travels, strains have become endemic swine, horses, humans, camels, dogs and humans. There are 16 hemagglutinin (H) and 9 neuraminidase (N) variations creating a total of 144 known strains that are endemic in specific species. However the virus the virus has been able to cross species frequently in the scope of evolutionary history.

In recent history, there have been several jumps between hosts that typically results in an exceptionally high infection rate since zero hosts in the new species have resistance. The flu made the ecological advantageous jump in 1956 from an avian species. This avian variant was nicknamed Asian Flu (type H2N2) and caused an estimated 1 to 4 million deaths from 1956 to 1958. This later evolved into the H3N2 variant known as the Hong Kong Flu in 1969. A swine flu variant migrated into the human population in 1976 causing scares worldwide. Currently the fear is of another avian flu variant affected the human population commonly referred to as Avian Flu. However it is unknown how successful the Avian Flu will be in jumping hosts. Perhaps most people remember the Spanish Flu that was deadly around WWI. Genetically little is known about the Spanish Flu; its considered type H1N1 and its origins are unknown. However it is the prime example of how ecologically successful the flu virus can be a migrating between hosts. The virus killed somewhere between 40 to 100 million people worldwide when it made a jump between hosts.