Animals able to pass, contract swine flu       

Written by Amanda Curry, Daily Vidette Senior Staff   
 
출처 : Monday, 16 November 2009 02:24 
http://www.videtteonline.com/index.php?option=com_content&view=article&id=30981:animals-able-to-pass-contract-swine-flu-&catid=37:newsnationalglobal&Itemid=53

In recent weeks, humans have not been the only mammals to contract H1N1. Several cats and ferrets have contracted the virus proving that animals are susceptible to swine flu as well.
“The influenza virus has molecules on its surface that allow it to attach to host cells.  Many species of animals have influenza, but usually a particular strain of the influenza virus is restricted to infect only its specific host,” Laura Vogel, associate professor of immunity, said.
“For example, we know that there is a canine influenza virus that can make dogs sick and spread from dog to dog, but people can’t get that strain of the virus.”

The H1N1 virus, however, has mutated so that it is able to attach to host cells of other animals and humans, thus infecting them with the virus.

“The problem is that influenza viruses can change their surface molecules, and when this happens, which is rare, the virus can infect a new type of host.  That is what happened in the case of H1N1, which seems to have properties of influenza viruses that would normally infect only birds, only pigs or only people.  This new mutated virus then can infect more host species.”

H. Tak Cheung, director of the school of biological sciences, explained the virus is much like a key and lock phenomenon.

“The virus must have the right key to open the right lock in order to get entry to the cells. The key that would unlock human or pig cells would not unlock the other type. However, imagine the key makers might make a tiny little error in making the key, and this is the result of mutation, a change in the genetic material of the virus…this slight change will allow, normally, a virus for a pig to fit humans. Now this virus crossed the species barrier.”

Humans are also able to pass the flu to animals through the same methods.

“Of course the same thing can go in the opposite direction, a virus normally for humans will be able to infect a pig, because of this change in the protein through mutation… The lock can also change, allowing it to fit the key,” he said.

“Primate cells are very similar to our cells and most human influenza viruses can infect other primates.  This is a rare event, but again not surprising since the virus can change its surface molecules,” Vogel said.

“The reason people worry is because it normally infects pigs, because it infects pigs, it has structures slightly different from a virus that would normally infect the human population,” Cheung said.

“If this virus crosses the species barrier, it might cause more serious infections because the population might not have immunity against this specific virus because it’s new and many people will be susceptible to it,” he explained.

“The influenza virus has a very, very high rate of mutation and this allows it to change rapidly… This change is responsible for the continuing threat of the influenza virus every season,” he continued.

“Normally the virus only changes slightly from one season to another when it is a human influenza virus, but then when you have a virus that jumps the species barrier, the population becomes far more vulnerable because it comes from another animal. This incidence of jumping across the species barrier does not occur frequently, but when it does occur, it creates a much greater threat as compared to the influenza viral strain that occurs in humans from one season to another.”

Vogel explained there are many diseases that spread between animals and people.  These are referred to as zoonotic diseases and include familiar diseases such as rabies and West Nile virus.

“At this time, there aren’t any reports of people catching the H1N1 from their pets and you are much more likely to catch it from an infected person,” she said.

“Don’t forget this virus is easily killed by basic sanitation methods like soap and disinfectants.  It is killed at normal cooking temperatures and not very stable on surfaces, so it is primarily spread through respiratory droplets.  The study of zoonotic diseases has become increasingly important with the emergence of new diseases like H1N1, West Nile and ‘bird flu.’”