As mentioned previously, oral herpes is usually transmitted through oral contact, such as kissing or sharing food or beverages with an infected person. Genital herpes infections usually result from sexual activity. However, you can get oral herpes (HSV-1) on the genitals and genital herpes (HSV-2) on the mouth through oral-to-genital contact. (The former is more likely than the latter.)
It's also possible to get HSV-2 on the genitals if you already have HSV-1 there, but it's not as common to get HSV-2 on the mouth if you already have HSV-1. The HSV-1 infection usually prevents HSV-2 from infecting the same area. In addition, genital HSV-1 isn't usually spread through genital-to-genital contact.
The site of infection also tends to influence how often the viruses reactivate. Away from their "home sites," HSV-1 and HSV-2 infections tend to be mild. Overall, there's no hard and fast rule about how often a person with HSV-1 or HSV-2 will experience an outbreak. Children and people with weaker immune systems may experience more outbreaks. Otherwise-healthy people may experience them rarely or only when exposed to certain triggers such as stress, prolonged exposure to sunlight or foods containing caffeine.
Neonatal herpes can result from either HSV-1 or HSV-2 infections, although HSV-2 is the most common. It occurs most often when the mother has an active outbreak and the baby is delivered vaginally. In newborns, herpes can affect the skin, eyes or mouth (SEM herpes); the central nervous system (CNS herpes); or other internal organs (disseminated or DIS herpes). Babies can have more than one type. CNS and DIS herpes have the highest incidence of death. The former can cause seizures and swelling in the brain, while the latter can lead to organ failure.
Pregnant women can avoid passing HSV-2 on to their newborns by delivering via C-section if they have an outbreak. They can also take medications to suppress their outbreaks. We'll look at treating and preventing the spread of herpes simplex viruses next.