How can the same virus cause different disease in different part of the body?

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Offline Lethalwolf

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Olivier asked the Naked Scientists:
Dear Chris and gang,

I love your show. I heard you on Dr Karl's show when you were in Australia and got hooked up to the naked scientist. I've been downloading your podcasts from the archives.

I have a question about the herpes virus, I thought it was only a sexually transmitted disease but found out cold sore are also cause by the same virus.

How can the same virus cause different disease in different part of the body? If l get infected in the eye for example, is that another disease as well? How about a vaccine, like for the flu since l suppose the virus doesn't mutate every year.

Thanks a lot

What do you think?


Offline Chelsie

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It is very common for there to be several forms of the same virus. For example, the common cold is caused by several different viruses. Once you've had a cold, you generally build up immunity so you won't usually become ill from the same cold virus again. Therefore, when you experience another cold in the future it is usually caused by a different type of cold virus.

The herpes virus you are specifically referring to is called herpes simplex, which is an infection that affects the skin and nervous system, and produces small temporary blisters on the skin and mucous membranes. There are two types of herpes simplex: Type I and Type II.

Herpes infection occurs when herpes simplex virus enters the body through the nose, mouth, genitals, open sores etc. and travels into human nerve cells. The virus can be inactive for years and may never wake up. The virus can become active due to a decrease in the immune system. This can be brought on by other illnesses, stress, surgery, some medications etc. 

Type I herpes (HSV-1) commonly causes the herpes blisters around the mouth. In some instances, type I herpes can cause blisters on genitals due to oral to genital contact. Type I is usually transmitted by kissing someone who has open herpes blisters, sharing a toothbrush, using the same lipstick etc. Type I can also cause Ocular Herpes in extreme cases.
Type II (HSV-2) cause genital herpes. You can get Type II during sexual contact with someone who has a genital HSV-2 infection. Some people may not be aware that they are infected thus easily spreading the virus to their partner if they are not using protection.

To wrap up your question:

A virus can come in different types which can lead to similar but slightly different infections. The area of outbreak depends on the type of herpes virus contracted, the origin of contraction (mouth, eyes, genitals etc.), and your immune system's ability to control the virus. The stronger your immune system, the less areas of breakout, whereas a weak immune system could result is large areas of your body being covered in blisters.
If I were an enzyme I would be DNA helicase so I could unzip your genes.