The 8 types of herpes: characteristics and associated diseases

These are the types of herpes, health disorders linked to Herpesviridae viruses.

Viruses are infectious agents by definition, and few biologists today classify them as living beings. They are segments of genetic information (DNA or RNA) covered by a capsid (nucleocapsid), which may or may not be surrounded by an envelope. Since viruses lack organelles such as ribosomes or mitochondria, they cannot grow or replicate on their own: to proliferate, they must infect a host cell and hijack its machinery.

By different mechanisms, a virus is able to enter a human cell, integrate its DNA (or transform its DNA into RNA first) into the nucleus, let the cell copy it and assemble itself as it leaves the host cell body. As you can imagine, in the lytic phase of the process, viruses kill the cell as they go out to infect others.

With this short tour through the viral cycle, we understand why they are all pathogens and why they cause damage to the tissues they infect. Based on all these premises, here we will see which are the types of herpesmore specifically, the viruses of the family Herpesviridae that can infect the human being.

What is a herpes?

According to the Oxford Languages dictionary, a herpes is an inflammatory disease of the skin, caused by a virus, which is characterized by the formation of small transparent vesicles or blisters that, when dried, form a kind of crust. The term "herpes" does not go beyond the clinical picture and, therefore, we see much more interest in citing the types of Herpesviruses, those agents that lead to various pathologies.

There are more than 100 types of Herpesvirusesbut all of them have a very similar structureThey consist of a double stranded DNA (without RNA intermediates), with a protein capsid, an intermediate tegument with viral enzymes and a glycoprotein membrane that delimits the virus from the medium. The diameter of these viral agents is 150 to 200 nanometers and the final membrane contains a series of glycoproteins (gB, gC, gD and gH), which bind to the receptors of the cell to be infected, to fuse both membranes.

The main types of herpes

Once we know the general form of herpesviruses and their diversity, it is time to explore the 8 types of agents of the Herpesviridae family that routinely affect humans. Don't miss them.

1. HHV-1

The herpes simplex virus HSV-1 or HHV-1 is one of two strains of the Herpesvirus family that can cause latent infections in the neurons of the sensory ganglia. (bulbous formations along the nerves of the autonomic nervous system or ANS). However, unlike HSV-2, this strain is usually acquired early in development, whereas HSV-2 is acquired through early sexual contact.

The World Health Organization (WHO) estimates that 3.7 billion people under 50 years of age are infected with this viral strain (67% of the population). It is the main cause of herpetic gingivostomatitis, also known as "cold sores".. These well-known lesions can appear on the palate, gums, tongue, lips or adjacent regions of the face.

At this point, it should be noted that the virus remains latent or quiescent in the neural ganglia, keeping the infected cells alive by interfering with cell apoptosis mechanisms. When the virus is reactivated by various triggers (other infections, stress, hormonal changes, etc.), cold sore symptoms appear again.

Another much more severe form of HHV-1 infection is herpetic meningoencephalitis.

2. HHV-2

This is the second strain classified within the "herpes simplex virus" group. The premise is very similar to the previous case, but this time, the most common clinical manifestation is genital herpes..

The infection presents with a symptomatic picture lasting up to two weeks, with ulcerative and painful lesions, which may recur.

An estimated 491 million adults (13% of the world's population) are infected with HHV-2. As it is transmitted by sexual contact under more specific conditions, the percentage of people affected is lower than with HHV-1.

3. HHV-3

We have now moved on from simple herpes simplex, and now move on to categories that are also familiar to you, albeit with lower epidemiological figures. HHV-3 is known as varicella-zoster virus (VZV), which, as its name suggests, causes chickenpox (in children) and shingles (in adults). (in children) and herpes zoster (in adults).

In the United States, the VZV virus was previously estimated to have infected 99.6% of people aged 40 years and older. Not surprisingly, the basic reproductive rate of this virus is one of the highest: it ranges from 10 to 12. This means that, on average, a sick person will infect up to 12 others before being cured. Fortunately, the vaccine against this virus has drastically reduced the epidemiological patterns of chickenpox in recent years.

4. HHV-4

Better known as "Epstein-Barr virus", this infectious agent is the major cause of acute infectious mononucleosis.. It is estimated that, by adulthood, more than 90% of people have been infected and have developed antibodies to the virus. Mononucleosis is known as the "kissing disease" because it is transmitted through saliva and remains viable for several hours in saliva.

Curiously, in children this infection is asymptomatic, causing at most a case of pharyngitis (with or without swollen tonsils). On the other hand, 75% of the adult population that is infected presents a case of mononucleosis, characterized by swollen lymph nodes, fever, tiredness and pharyngitis.

5. HHV-5

HHV-5 or cytomegalovirus (CMV) is found in many mammalian species and, in humans, is another cause of infectious mononucleosis. In countries such as the United States, it is estimated that 50 to 85% of the adult population is infected.. However, the vast majority of immunocompetent persons experience no or minimal symptoms after contact with the pathogen.

The problem occurs with immunocompromised persons, because like other Herpesviruses, this agent can remain latent and reactivate when the host immune system is weak. Cytomegalovirus is also of some clinical importance in the obstetric setting, as it can cause fetal complications (in very rare cases).

6. HHV-6

HHV-6 is rather less well known than others on this list. This infectious agent can be divided into two subtypes: HHV-6A (human lymphotropic virus) and HHV-6B (causing infantile roseola).. In any case, HHV-6B is the most clinically relevant, since in European regions it causes more than 90% of infections of this type.

HHV-6B infection in children manifests as transient skin rashes, which appear after 3 days of fevers. It is much more common in infants between 6 months and 3 years of age and is not usually treated as a major clinical entity.

7. HHV-7

This virus is very similar to the previous one. Although most cases of roseola are caused by HHV-6, HHV-7 has also been isolated in some patients.

8. HHV-8

This virus is atypical like few others, as it causes cancer, no more and no less. It is the cause of Kaposi's sarcoma, a malignant tumor of the lymphatic endothelium, typical of immunosuppressed persons. typical of immunocompromised individuals, which usually presents in the form of blotchy lumps on the skin (although it can also affect the Gastrointestinal tract or the lungs).

We will not explain the complex process that induces malignant neoplasia at the site of infection, since it is sufficient to know that this virus possesses a series of homologous genes that, by acting with the host cell, promote it to become cancerous.

Summary

Surprising, isn't it? Herpesviruses are a fascinating family of viruses, and they go far beyond the cold sores we tend to associate them with. While the herpes simplex viruses HHV-1 and HHV-2 are associated with oral and genital herpes respectively, many others present with different clinical pictures.

What is clear is that, with few exceptions, herpesviruses are cosmopolitan, infecting people all over the world regardless of their status, and we have probably all been infected with at least one of them. Fortunately, our immune system is capable of keeping them at bay in normal situations.