Herpes viruses comprise a large family of DNA containing viruses which affect both animals and human. These viruses tend to persist in the body for the whole life, causing periodic disease recurrences.
Herpes simplex viruses 1 and 2 are also known as Herpesvirus hominis, they belong to the alpha herpesvirus group. HSV possesses an internal core with a linear double-stranded DNA. The capsid of herpes viruses consists of 162 consumers. The virus is wrapped in a lipid envelope with viral glycoproteins on the surface. Its molecular weight is approximately 100×106 units and diameter of approximately 160 nm.
Both HSV-1 and HSV-2 cause common infections with variable clinical manifestations in otherwise healthy individuals, whilst these infections tend to be more severe in immunosuppressed children and adults.
HSV-1 is transmitted by oral-to-oral contact and exposure to infected saliva, whereas HSV-2 is a sexually transmitted infection. No animal reservoirs are known.
Although HSV-1 is considered to cause herpes labialis, it may affect any organ and in at least 50% of cases manifests with genital lesions.
By the age of 50 almost 90% of adults are infected with HSV-1. It was estimated that every year in the world occur more than 23 million of new HSV infections.
HSV-2 is more common for females than males. Usually HSV-2 infection is associated with the onset of sexual activity. The global prevalence of HSV-2 was about 11,3% as of 2012. About 23 million of new cases of HSV-2 are observed every year.
Herpes simplex virus is able to affect all the organs and membranes of the body. The incubation period may last from 1 up to 26 days (usually 6-8 days).
Specific features of HSV infection include the following:
- The ability of HSV to replicate and remain in the nervous system;
- The virus remains in the ganglia – when orofacial lesions appear the virus is found in the trigeminal ganglia, in case of genital herpes – in the sacral nerve root ganglia.
- The infection tends to reactivate induced by fever, traumas, stress, impaired immunity.
Causes of rash
The virus causes ballooning of the epithelial cells, the cellular membranes are damaged and the formation of giant cells with multiple nuclei follows. This results in the development of vesicles which contain clear fluid. Around these vesicles occurs erythema due to inflammatory response. As the time passes the fluid in the vesicles become purulent. Scarring occurs rarely.
The ulcers are more common for the mucous membranes because of their epithelium fragility in these regions. However, the lesions of the mucosa are formed via the same processes as the skin lesions.
Viruses later travel to the ganglia via the nerves where they remain for all individual’s life (known as infection latency) and may cause disease recurrence under certain circumstances (reactivation of the virus induced by fever, traumas, immunosuppression, emotional stress etc.).
Risk factors for herpes labialis recurrence
- physical or emotional stress;
- exposure to ultraviolet light,
- tissue damage;
- immune suppression;
Risk factors (herpes genitalis)
- Sexually active lifestyle;
- Negroid race;
- Big number of sexual partners;
- Poverty or low income;
Primary infections are usually last longer and tend to involve several organs and cause complications than HSV recurrence. However, in individuals with affected immune system (for example, those who have AIDS) the course of the infection reactivation is severe, prolonged and widespread.
Read more: Herpes simplex
Approximately 80% herpes simplex virus infection is asymptomatic. Herpes simplex virus has been reported to affect nearly all internal organs and mucosal sites. Symptoms of the infection depend on the anatomic site, person’s age and his/her immune system as well as the type of the virus (HSV-1 or HSV-2). Some illnesses caused by HSV may be even life-threatening.
Oral and facial symptoms
The average incubation period of HSV-1 is 4 days with a range from 2 to 12 days.
Primary HSV-1 infection typically manifests with gingivostomatitis and pharyngitis. This usually happens in young children between 1 and 3 years of age. When the lesions appear a person experiences fever, sore throat malaise, itching, burning sensations, myalgias, inability to eat, irritability, cervical adenopathy, and mucosal edema. Tingling and pain may precede the occurrence of sores.
Vesicular rash which looks like small blisters is distributed on the hard palate, the tongue, the gingiva, and around the lips. These lesions, also known as fever blisters or cold sores tend to rupture, leaving gray-white ulcers. The disease lasts from 10 to 21 days.
The virus may be found in oral secretions from 7 to 10 days as well as in the stool.
When the disease recurs the pain, burning, tingling or itching sensations precede the development of the orofacial lesions.Within 24-48 hours afterwards the painful vesicles appear, typically on the border of the lip. From 3 to 4 days later the vesicles crust and after 8-10 days the lesions disappear.
Central nervous system lesions
The virus may spread into the brain via the ganglia and results in HSV encephalitis. HSV encephalitis presents with headache, fever, altered consciousness, seizures, memory loss, anosmia (absence of the smell perception), olfactory hallucinations, speech disorders, and behavioral disturbances.
HSV meningitis is usually associated with genital herpes.
HSV-1 infection was reported to be related to Bell’s palsy – the paralysis of the mandible.
The incubation period of primary genital herpes may last from 2 to 12 days. Primary genital herpes tends to have a prolonged symptom duration.
The first episode of genital herpes manifests with fever, headache, general malaise, and muscular pain. Pain, itching, dysuria, vaginal and urethral discharge, and the painful enlargement of the local lymph nodes are characteristic. These symptoms occur between day 7 and 11 of the illness.
Widely spaced bilateral lesions on the genitalia are observed on examination, including vesicles, pustules, painful erythematous ulcers, and crusting. The lesions persist for approximately 21 days. However, in males the lesions heal faster.
A clear mucoid discharge and dysuria (painful urination) may also be present. The cervix and urethra are involved in more than 80% of women with first-episode HSV. Women are likely to experience more severe primary infections and tend to develop various complications.
The onset of primary herpes genitalis in males appears as a cluster of vesicles on the red surface of the skin on the glans or shaft of the penis.
In females the lesions appear on the two sides of the vulva. Cervicitis commonly develops. The painful lesions quickly become ulcers and are covered with a gray-white exudate.
Recurrent herpes genitalis usually lasts less than the primary infection with the duration of 7 to 10 days and the rash is not so abundant. Several hours prior to a recurrence itching, burning, tingling, or tenderness may be observed.
In males the lesions typically are observed on the glans, or shaft, of the penis. In females the labia minora, labia majora, and perineum are the most frequently affected.
HSV-1 infection of the finger is known as herpetic whitlow. It occurs when the broken skin of the hand is exposed to the virus. An infected finger swells and becomes reddish acutely, it becomes tender and painful. Vesicles or pustular lesions are detected on the fingertip.
Herpes gladiatorum (mat herpes) is common for wrestlers and other sportsmen involved in high-contact sports. This type of HSV 1 infection develops due to the traumas of the mucosa and the skin as the virus penetrates through the injured epithelium. It may affect almost every part of the body.
HSV causes keratitis – an inflammation of the cornea. It manifests with pain, blurred vision, and chemosis. Characteristic dendritic lesions of the cornea are detected. Blepharitis and follicular conjunctivitis may also occur.
In newborns and those who has impaired immune system (HIV-positive individuals) chorioretinitis may develop.
Internal organs affection
Multiple organs may be involved. However, the esophagus, lungs and liver are commonly affected.
HSV esophagitis causes odynophagia (pain while swallowing), dysphagia, substernal pain, and weight loss. The distal part of the esophagus is usually affected.
HSV infection causes pneumonitis or tracheobronchitis. HSV hepatitis may be seen in individuals with the suppressed immune system. Hepatitis manifests with the sudden increase of bilirubin and aminotranspherase levels and fever.
HSV infection may also affect the joints, adrenal glands pancreas, small and large intestines, and bone marrow.
- disease localized to the skin, eye, and/or mouth (SEM) (45% of cases);
- encephalitis, with or without SEM involvement (30% of cases);
- disseminated infection when multiple organs (the CNS, lung, gastrointestinal tract, liver, adrenals, skin, eye, and/or mouth) are involved (25% of cases).
30% of neonatal HSV occur due to HSV-1 and 70% to HSV-2. 65% of neonates die as a result of HSV infection if not treated.
The diagnosis is made based upon clinical features and laboratory tests such as DNA or PCR tests and virus cultures.