Herpes

One of the most common viruses throughout the world is the herpes simplex virus; this is categorized into herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). Globally, nearly 4 billion people under the age of 50 have HSV-1; once a person contracts the virus, they will have it for the duration of their life. Fewer than 500 million people around the world have HSV-2; this variant is a sexually transmitted infection and is not as easily spread from person to person.
HSV-1 is primarily spread through oral contact; when a person has close oral contact with an infected person, whether symptomatic or not, they are at risk of contracting the virus. Oral-to-genital contact can spread HSV-1 to the genital area, as well. HSV-2, however, is almost entirely transmitted during sexual activity involving genital-to-genital or genital-to-anal contact. Individuals can go for lengthy periods of time without experiencing any symptoms of either variant of the infection; when symptoms do manifest, they often cause blisters or sores at the site of infection, sometimes resulting in severe pain.
As mentioned, there is no cure for an HSV infection; the symptoms of the virus, though, can be addressed through the use of antivirals such as acyclovir and famciclovir. As with many infections, the best treatment is prevention - the regular and correct use of condoms can prevent the spread of HSV-2, and avoiding oral contact - either directly or indirectly, such as through sharing things like lip balm - with individuals displaying active HSV-1 symptoms can stop the spread of this more common form.