Cold sores are caused by certain strains of the herpes simplex virus (HSV). HSV-1 usually causes cold sores. HSV-2 is usually responsible for genital herpes. However, either type can cause sores in the facial area or on the genitals. Most people who are infected with the virus that causes cold sores never develop signs and symptoms. The herpes simplex virus usually enters the body through a break in the skin around or inside the mouth. It is usually spread when a person touches a cold sore or touches infected fluid-such as from sharing eating utensils or razors, kissing an infected person, or touching that person's saliva. A parent who has a cold sore often spreads the infection to his or her child in this way. Cold sores can also be spread to other areas of the body. In Norway we analyzed prospectively the proportion of HSV-1- or HSV-2-positive culture samples from our sexually transmitted disease clinic outpatients with genital herpes infection during the years 2003 to 2012 and compared the proportions of positive HSV-1 and HSV-2 findings with the age and sex of the patients.
Results: Herpes simplex virus type 2 was typed in 66.4% (557/839) and HSV-1 in 33.6% (282/839) of the patients during the entire study period. The mean age of male patients (26.3 years) with a laboratory-confirmed HSV-1 infection was significantly lower than that in male patients with anHSV-2 infection in 2003 to 2007 (26.3 vs. 32.9 years), with P < 0.0001, and (28.6 vs. 34.0) P < 0.0019 in 2008 to 2012, respectively. More female than male patients had HSV-1 infection; in the first study period (2003-2007), 58% were female, and in 2008 to 2012, it was again 63.6%. There was no significant difference between the age of female patients with HSV-1 and those with HSV-2. Various vaccine candidates have been developed, the first ones in the 1920s, but none has been successful to date. Due to the genetic similarity of both herpes simplex virus types (HSV-1 and HSV-2), the development of a prophylactic-therapeutic vaccine which is proven effective against one type of the virus would provide fundamentals for vaccine-development for the other virus type. As of 2015, several vaccine candidates are in different stages of clinical trials as they are being tested for safety and efficacy, including at least three vaccine candidates in the US and one in Australia.