It's a beautiful day and you're outside enjoying the fresh air. You feel a small prick on your arm and notice that a mosquito is getting a free meal. Without realizing, you kill it with a quick slap of your hand, but notice a little blood on your arm where the mosquito was. Along with the nuisance of a mosquito bite, you might be worried about possible infections you can catch, including hepatitis.
It's intuitive to think that when a mosquito bites someone infected and then bites another person, the second person could be exposed to viral hepatitis. Fortunately, viral hepatitis isn't spread from mosquitoes. Let's look at some reasons why.
Mosquitoes Inject Saliva, Not Blood
Because hepatitis B and hepatitis C are spread by contact with infected blood, it's very tempting to think of mosquitoes as flying hypodermic needles. However, the "needle" that mosquitoes feed with, called the proboscis, is actually a complex structure that has separate channels. When a mosquito bites, it injects saliva through one channel. The saliva functions as a lubricant to help the mosquito feed easier. The blood it sucks as a meal flows in a completely separate channel and only in one direction: toward the mosquito. So, it's biologically unlikely for infected blood to be spread to another person.
But, Wait! Mosquitoes Spread Malaria and Yellow Fever. Why Not Hepatitis?
Since mosquitoes can spread some diseases, such as malaria and yellow fever, it is tempting to think they can spread other blood-borne diseases like HIV and hepatitis. The answer is in the saliva! When a mosquito bites, it injects its own saliva into whatever it is biting. The diseases spread by mosquitoes are actually spread through the mosquito's saliva. Hepatitis, however, is spread through blood.
Need More Proof? Viruses are Fragile
The hepatitis viruses are very picky about what they infect and where they can survive. They really like livers, and mosquitoes don't have livers! This means that the mosquitoes aren't really a good home and the viruses wouldn't survive long enough to be spread, even if they could be. Also, people who study mosquitoes have noticed they usually don't bite two people consecutively. After they bite, they will fly away to let their food digest and then after a period of time, they will feed again. Because the hepatitis viruses don't last long in a harsh environment, they wouldn't survive long enough to infect.
So, Is this Just Mosquitoes? How about Insects and Spiders?
Mosquitoes are part of a very diverse biological classification called arthropods, which include a variety of life. Some types of arthropods include insects, spiders, centipedes, shrimp and crayfish. Experts agree that arthropods don't spread viral hepatitis. A fair bit of scientific study has gone into how arthropods spread disease, especially since HIV emerged in the 1980s.
If Not Mosquitoes, What Does Spread Hepatitis C?
Hepatitis C is spread by direct contact with infected blood. So, some things that could expose you to infected blood would be razors, needles (not mosquitoes!) and toothbrushes. Also, certain actions are at higher risk for spreading hepatitis C. Examples of these would include injecting street drugs without sterile needles and works and having sex with someone who is infected (though this doesn't happen often).
Question: How long does the hepatitis virus live outside the body?
Answer: Many viruses cause hepatitis, but only five common viruses share an affinity for infecting the liver. These are known as hepatotrophic viruses and are usually what people mean when they talk about hepatitis viruses. While they cause similar symptoms in the body, they are separate viruses and have different characteristics. All of these viruses can be infectious outside of the body for certain periods of time. However, a good rule of thumb is that wet material is infectious and dried material is much less infectious.
The hepatitis A virus, or HAV, is relatively hardy. In good conditions, it can survive outside the body for months. HAV can survive certain acids and some heat. For a period of time and under certain conditions, HAV can survive in sea water, dried feces and live oysters.
Hepatitis B Virus
The hepatitis B virus, or HBV, can still be infectious for up to a week outside the body.
Hepatitis C Virus
The hepatitis C virus, or HCV, can live outside the body for up to 4 days. However, many experts think it usually survives up to 16 hours at room temperature.
Hepatitis D Virus
This virus needs help from the hepatitis B virus to be infectious, so it only infects someone with hepatitis B.
Hepatitis E Virus
This virus is spread similar to the hepatitis A virus and causes acute disease similar to the others.作者: 天使的羽毛 时间: 2009-6-18 22:41