The abbreviation ECHO in the name of echoviruses stands for Enteric Cytopathic Human Orphan. It is a virus in the enterovirus family that causes gastrointestinal infections, skin rashes, and neurologic and flu-like symptoms. In most cases, echoviruses enter the human circulation through the digestive tract. Other ports of entry include the respiratory tract and fecal-oral transmission. Echoviruses are characterized by high environmental resistance.
What are echoviruses?
Echoviruses are nonenveloped, spherical RNA viruses that belong to the enterovirus genus. Like coxsackie and polioviruses, they are classified in the Picornaviridae family. Human echoviruses, whose reservoir (host) is humans, are grouped under the species Human Enterovirus B (HEV-B) in the molecular classification (Humana Enteroviruses HEV A-D). A total of 27 serotypes are distinguished, with types 22 and 23 assigned to the genus Parechovirus. This virus is one of the many viruses that preferentially affect the gastric tract. After rhinoviruses, which cause cold symptoms, enteroviruses are the most common virus species in humans. The name “orphan” comes from the fact that echoviruses were first discovered in the 1950s without any clear association with other infectious diseases. Echoviruses cannot be clearly assigned pathogenetically or systematically.
Occurrence, distribution, and characteristics
The name “Picornaviridae” is derived from the size of this viral genus, as the individual viruses are just 22 to 30 nm in size and are among the smallest of their kind. The other parts of the name describe an enteric, cytopathic and human virus. Echoviruses are found worldwide, but mainly in countries with low socioeconomic infrastructures, with lower hygiene and contaminated sewage playing a major role. In countries with temperate climates, echovirus infections occur predominantly in summer and fall. Common serotypes such as type 30 are also detected year-round. Some virus types, such as Echo 13 and Echo 18, can cause increased meningitis outbreaks after a prolonged latency period. In most cases, echovirus enters the human circulation via the lymphoid organs and epithelia of the pharynx and digestive tract. There it multiplies and subsequently spreads to surrounding tissues. Further possibilities of infection with the echovirus exist via smear infection through fecal-oral transmission as well as via the respiratory tract by droplet infection. Contaminated hands play a decisive role here. Indirect transmission occurs via virus-contaminated objects, bath water or food. The viruses spread on all objects that come into contact with the hands and contaminated feces and can survive there for a long period of time. Echoviruses have a particular affinity for cardiac muscle tissue and therefore exert a cardiotropic (affecting the heart) effect. The most common subtype in antibody detection is echovirus 30. After successful replication in the digestive tract, echoviruses spread throughout the body and can cause serious central nervous system disease. Infection of the lungs, spleen, liver and bone marrow is also possible. Infected people excrete echoviruses in their stool for several weeks. A vaccine is not yet available, but the risk of infection can be reduced by regular hand washing and careful hygienic measures when preparing and eating peeled fruit and cooked foods.
Diseases and ailments
For children and adults with a healthy immune system, echovirus infection is usually harmless if treated promptly. Often, infected people do not feel any symptoms because a healthy immune system is usually able to fight off an infection with echoviruses. Those who have once undergone an infection with enteroviruses develop type-specific immunity. If symptoms develop nevertheless, patients experience mild, neurological symptoms with fever and skin rash, as well as summer flu-like accompanying symptoms. Other mild accompanying symptoms include sore throat and dry, irritating cough.In its generalized disease, pneumonia, encephalitis, myocarditis, pericarditis, and blood poisoning may occur, with Echo 11 being considered particularly dangerous. Echo 7, 11, and 70 are often accompanied by conjunctivitis, and Echo 6 and 9 mainly cause pleuritic pain and muscle aches. Viral meningitis is the most common clinical picture, which can cause chills, nausea, stiff neck, headache, and sensitivity to light. Usually, symptoms resolve within two weeks without complications. Children and infants often have a particularly irritable reaction. Complications during pregnancy have not been reported with echovirus infection. In infants, this infection is rarely fatal if it remains undetected or treatment begins too late, since it settles preferentially in the heart or liver and often sufficient antibodies have not yet been formed. Although children and infants are more at risk than adults, the course of the disease is less severe in them. The average incubation period is 7 to 14 days, but a latency period of 2 to 35 days is also possible. Treatment, which is purely symptomatic and targeted to the affected organ system, is with antivirals that inhibit the multiplication and release process of the bacteria. Gamma globulins are used in severe cases of disease. However, tests specifically directed at echoviruses are not performed because the course of the disease is usually not serious. Diagnosis is made by rectal swab, throat swab, stool sample, or spinal fluid examination. A differential diagnosis must be made here with other enteroviruses that can cause similar clinical pictures.
