The simple answer to that question is “yes.” Cold sores are extremely contagious. In fact, it’s estimated that 80 percent of the adult population in the U.S. is infected. The more complex answer is that they are more contagious during some parts of the outbreak than others, and that there are things you can do to minimize the chance of being infected or, if already infected, of infecting others.
Herpes Simplex Type I
Cold sores are caused by a type of herpes virus, Herpes Simplex Type 1. This is the same general family of viruses that causes genital herpes, chicken pox, and shingles (although the latter two are caused by a herpes zoster virus less closely related to the virus that causes cold sores).
The herpes simplex virus produces the symptoms of blisters and open sores, usually in the area of the mouth, that characterize an outbreak. After the sores heal, the virus retreats along the nerves of the face and goes into dormancy, producing no symptoms. Any weakening of the immune system can produce a fresh outbreak at any time, however.
Are Cold Sores Contagious When Dormant?
Herpes is still contagious during dormancy. In other words, there is no safe time for contact between an infected and uninfected person, during which transmission of the disease is impossible. However, the risk of infection is much less during the dormant phase than during an outbreak.
During An Outbreak
The virus becomes especially contagious during an outbreak. The outbreak follows the following sequence. An itching or burning sensation usually precedes visual symptoms. Reddened and swollen skin follows. The skin forms tiny fluid-
The fluid that leaks from the open sores is packed with live viruses, so this stage of the outbreak represents the peak of contagion. During the entire outbreak, however, the virus has risen to the skin surface, which increases transmission chances. The virus can be conveyed by direct or indirect touching, and if droplets of fluid are involved it may become airborne (although it’s normally not directly airborne like the flu). For a few days after visible symptoms disappear, the chance of infection remains elevated. After this, it returns to the smaller infection chance that exists during dormancy.
Types Of Contact
The main way that the virus is spread is by direct or indirect contact between the sufferer’s infected area and a susceptible area of someone else’s body, usually meaning the mouth region. Kissing an infected person, especially while an outbreak is ongoing, is a common avenue of infection. It’s also possible to carry the virus by hand. The hands are not a very good breeding ground for the herpes virus, but the virus can
survive there long enough to make contact with the mouth area.
The herpes virus can also be transmitted by oral sex, in either direction. That is, someone with cold sores performing oral sex on someone else could infect the other person with genital herpes lesions, and performing oral sex on someone with genital herpes could result in infection with cold sores. Usually genital herpes is caused by Herpes Simplex Type 2 rather than Type 1, but that isn’t an ironclad rule. Either version of herpes can cause symptoms in either part of the body.
Precautions
To minimize the chance of contagion, it’s recommended that sufferers of cold sores keep sores covered during an active outbreak (especially during the open sore phase) and wash their hands frequently to reduce the chance of secondary contagion. There is no way to completely eliminate the chance of transmission.