Almost everyone has experienced herpes on the lips (cold sores): small, painful blisters that heal after a time, but can always return. Herpes is caused by viruses. If you have been infected once, the viruses remain in the body for the rest of your life and can cause herpes blisters at any time.
Herpes can also break out in other parts of the body, primarily in the genital and anal region.
The herpes blisters can sometimes spread to a large area in HIV-positive people. The illness is more often severe in people with starkly compromised immune systems, leading to inner organs or the brain being affected. If that happens, herpes can be life threatening.
The risk of passing on HIV is increased with a herpes infection, as the herpes blisters contain a high concentration of HIV. HIV-negative people with a herpes infection can become infected with HIV more easily because the virus can enter the body more easily through the damaged mucous membranes.