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Parechovirus is a recently classified genus of virus that is closely related to enterovirus. This virus belongs to the Picornaviridae family and has two subtypes: Parechovirus A and Parechovirus B. Of these, Parechovirus A is the most common human pathogen and is called as human parechovirus (HPeV). They are small positive-sensed RNA viruses that are non-enveloped and single-stranded.
The infections that can be caused by a human parechovirus can range from mild diarrhea and gastric problems to serious infections like sepsis or meningitis. The 19 different types of human parechoviruses (HPeV 1 to 19) that are discovered till date vary in their characters and infections caused. Although infants and children are the most vulnerable group, people at any age can get infected by these viruses.
Human parechovirus infects people at any age and the infection can occur at any time of the year with temperate climates, especially in summer and fall. They are transmitted from one person to the other very easily through direct or indirect contact with respiratory fluids or fecal matters of the infected person. Secondary infection is the cause for more than 50% of the easily affected population. The most efficient transmitters are infected infants, particularly those that use diapers.
Once they enter into the host’s body, the virus first reaches the epithelial cells of the oropharynx and intestinal mucosa. There is a chance of replication of the virus in the nasopharynx, spreading it to the upper respiratory tract.
Most of the viruses get swallowed and reach the stomach and the gastrointestinal tract. Viral replication is most active in the Peyer’s patches in the lamina propria after passing through the intestinal lining cells.
Through the bloodstream, the virus gets transmitted to other parts of the body, thus causing meningitis or encephalitis or other tissue infections like myocarditis or pleurodynia. There is no chance of tracing the virus unless the infections become visible. Also, there is a chance of the virus spreading through the feces and respiratory system even several weeks after primary infection.
Human parechovirus, especially HPeV 3 is known to affect infants and small children more than any other age group. Most of the infections in infants are serious and cause infant sepsis, infant meningitis, encephalitis, transient paralysis, diarrhea, neonatal hemorrhage-hepatitis syndrome, hemophagocytic lymphohistiocytosis-like syndrome, myalgia, uveitis, and sudden infant death syndrome.
When compared with firstborns, later-borns show more chances of contracting infections at an earlier age. The dose of infection, as well as the severity of clinical symptoms, is greater in the later-born, particularly when the age gap between both is less than 3 years. This happens due to the intimate frequent contact within siblings.
The diagnosis of the infections caused by the virus is done on the basis of the symptoms alone. There is no possibility of identifying the virus in the body unless the infections become visible, as the viruses are normally asymptomatic in nature.
Also, there is no specific treatment for the virus and is purely supportive of the type of infections caused. If the virus is traced in the initial stages itself as in the case of infants, it can be treated easily with proper medical care. Otherwise, in serious cases, it takes years to completely come out from the infection.
There is a chance of reinfection with the virus (not specifically the same type) within three years of the first infection. There is no vaccine found yet for preventing human parechovirus infections. It is a difficult task as it has many subtypes and the infections caused vary in nature and characteristics.
Prevention is always better than cure. And in this case, as mentioned above, lack of proper treatment and the severity of some infections shows that prevention is the best choice. A few methods for prevention are listed below: