There are over 100 known herpes viruses. However, there are only eight herpes viruses that routinely only infect humans, which is why they are known as human viruses 1 to 8.
General Characteristics of Herpes Viruses
These have at least three characteristics in common:
1. Typical morphology with an icosahedral capsule of 162 capsomeres, covered with a viral envelope.
2. Genome of a DNA molecule, 120 to 250 kbp.
3. The productive phase of infection is followed by a latency phase in which the viral genome remains safely within the host's cells throughout the infected individual's lifetime. They can then undergo reactivation processes and give rise again to a productive phase in which numerous viral proteins are released.
The Eight Herpes Viruses That Routinely Only Infect Humans
Herpes Simplex Virus
Symptoms: An eruption of painful vesicles that evolve to scabs is associated with other manifestations such as fever, general malaise, fatigue, and neuropathic pain (dull, sometimes electric, and very unsettling).
Pathogenesis: The virus begins to replicate in the epithelium cells, thus causing the characteristic lesions of the disease. Later, the virus migrates through the nerves until it reaches the spinal ganglion, where, after a period of replication, it becomes dormant. When a reactivated infection occurs, the virus spreads from the dorsal ganglion to the epithelial and mucosal tissues, where it generates new skin lesions.
Epidemiology: The areas of highest prevalence are Africa and America. The area with the lowest prevalence is Asia. The countries with the highest incidence are those of Sub-Saharan Africa, with 80% of infected people under 35 years of age. It is the most commonly transmitted sexually transmitted disease (22%) in the United States of America. Its incidence is from 0.8 to 5.1 people per year. However, most people are asymptomatic.
Symptoms: First, there will be an itching sensation on the skin, and 4 or 5 days later, redness of the skin in that area on which vesicles sprout that are arranged in groups. After 7 to 10 days, the lesions dry out, forming yellowish-brown crusts that, when healed, sometimes leave a residual scar. The most frequently affected parts of the body are the trunk, thigh, or eye region.
Pathogenesis: It is a neurotropic virus with the ability to invade and reside in neuronal tissue. The varicella-zoster virus manifests as chickenpox, which is a contagious and benign disease; the virus replicates in the lymph nodes, spleen, and liver and then goes into a state of latency in the spinal nodes and, later, when reactivated, manifests as herpes zoster or shingles.
Epidemiology: The incidence rate is between 1.3 and 5 cases per 1000 people each year. Although it is possible for the disease to occur at any age, even in children, more than 66% of cases arise in subjects under 50 years of age and less than 10% in over 20-year-olds.
Symptoms - Pregnant women are the most susceptible to contracting it; however, it is a mild infection or without symptoms (the mother does not realize that she is suffering from it because she does not feel sick). Most fetuses that become infected have no repercussions at birth, but a small percentage may have cerebral palsy, microcephaly, deafness, seizures, learning difficulties, lung problems, anemia, or ocular problems.
Pathogenesis - The virus is excreted in breast milk, saliva, and urine. Cytomegalovirus (Human Betaherpesvirus 5) replicates in salivary glands and kidney cells, often resulting in cell fusion in multinucleated giant cells.
Epidemiology - It has a high worldwide prevalence. In underdeveloped countries, 90% of the population is infected, while it is 60% in developed countries.
Symptoms - It produces general malaise, headache, asthenia, myalgia, or abdominal pain, although sometimes the onset is sudden or acute, and the patient suddenly has a high fever.
Pathogenesis - It infects the epithelium of the oropharynx and salivary glands and replicates in these cells. B cells are infected in contact with these epithelial cells, while lymphocytes are directly infected. The virus then spreads through the bloodstream. Lymphocytes proliferate in large numbers, with an enlargement of the lymph nodes and spleen.
Epidemiology - When the infection occurs during youth, it causes infectious mononucleosis in 30-70% of cases.
Human Herpesvirus 6 and 7
Symptoms: Both viruses are related to roseola, which includes symptoms such as fever, skin rashes, swollen glands in the neck, sore throat, runny nose, cough, irritability, diarrhea, poor appetite, and swollen eyelids.
Pathogenesis: The infection process of these two viruses has been studied very little.
Epidemiology: This disease is probably the most frequent exanthematic disease in the first two years of life. However, it seems to have a low degree of contagiousness; endemic diffusion with permanent immunity is possible. Newborns probably have mother-borne immunity that lasts for six months.
Human Herpesvirus 8
Symptoms: Fever, increased C-reactive protein, adenomegalic syndrome, splenomegaly, edema, pleural effusion, ascites, cough, nasal obstruction, xerostomia, central nervous system symptoms, jaundice, autoimmune hemolytic anemia, and sarcomas.
Epidemiology: The prevalence in the world population has been estimated between 2 and 8%, but only with the outbreak of the HIV epidemic and the immunosuppression that causes (AIDS) has Kaposi's sarcoma become relatively frequent.
Herpes Virus B
Symptoms: It manifests, after an incubation period of between 2 days to 5 weeks, with a vesicular eruption located near the inoculation point; Along with the rash occurs fever, myalgia, headaches, and nausea. The vesicular rash is clinically and pathologically similar to that caused by the herpes simplex virus. After 3-7 days, neurological symptoms appear, such as meningism, nausea, vomiting, persistent headaches, confusion, diplopia, dysphagia, vertigo, dysarthria, cranial nerve palsy, ataxia. Later, a flaccid paralysis occurs in the lower extremities, extending to the upper extremities and chest, often leading to death, even with antiviral treatment, from respiratory failure.
Pathogenesis: The main mechanism of transmission is through bites or scratches from infected macaques (zoonoses). The virus enters the body and is transported through the nervous system to the brain.
Epidemiology: The disease reservoir is found in macaques from India and Southeast Asia. Stress in monkeys causes virus reactivation and its expression by saliva. Although contagion is rare, it is crucial to follow wildlife management guidelines when working with these animals.
The name "herpes" refers to a group of viral infectious diseases caused by the various viruses of the Herpesvirus family.
All types of herpes are infections caused by viruses and have the common characteristic of being highly contagious and resistant. Once they become established in the body, they are permanent, except for the most severe type, herpes zoster. Symptoms usually disappear and reappear when the immune system is weakened, such as in times of stress. But it can also be symptomless, which makes it very difficult to diagnose.
Herpetic Whitlow (or Whitlow Finger) is a viral infection where small blisters form on the fingers and the fleshy area around the fingertips. These sores or wounds are uncomfortable and painful, and they grow after direct contact with an infected source. The herpes simplex virus (HSV) causes this infection. There are two types of HSV. Type 1 usually affects the area around the mouth, lips, and face, while type 2 usually affects the genitals. Because herpes whitlow is caused by the same virus responsible for cold sores and genital herpes, it is extremely contagious. For that reason, it is essential that you recognize the symptoms of this condition and take steps to protect yourself.