enterovirus n : any of a group of picornaviruses that infect the gastrointestinal tract and can spread to other areas (especially the nervous system)

English

Noun

1. Any of many viruses, of the genus Enterovirus, that infect the gastrointestinal tract

The enteroviruses are a genus of (+)ssRNA viruses associated with several human and mammalian diseases. Historically the most significant has been the Poliovirus (which is now nearly extinct). Other types are coxsackie and echovirus.

Enterovirus are the most common cause of aseptic meningitis and can cause serious disease especially in infants and the immunocompromised.

"Human enteroviruses (family Picornaviridae) infect millions of people worldwide each year, resulting in a wide range of clinical outcomes ranging from unapparent infection to mild respiratory illness (common cold), hand, foot and mouth disease, acute hemorrhagic conjunctivitis, aseptic meningitis, myocarditis, severe neonatal sepsis-like disease, and acute flaccid paralysis. In the United States, enteroviruses are responsible for 30,000 to 50,000 meningitis hospitalizations per year as a result of 30 million to 50 million infections. Serologic studies have distinguished 66 human enterovirus serotypes on the basis of an antibody neutralization test, and additional antigenic variants have been defined within several of the serotypes on the basis of reduced or nonreciprocal cross-neutralization between prototype and variant strains. On the basis of their pathogenesis in humans and experimental animals, the enteroviruses were originally classified into four groups, polioviruses, coxsackie A viruses (CA), coxsackie B viruses (CB), and echoviruses, but it was quickly realized that there were significant overlaps in the biological properties of viruses in the different groups. The more recently isolated enteroviruses have been named with a system of consecutive numbers: EV68, EV69, EV70, and EV71."

Transmission

Poliovirus, as well as coxsackie and echovirus are faecal-oral spread (compare with entero- - relating to the intestines).

Species and genetics

Enteroviruses are members of the picornavirus family, a large and diverse group of small RNA viruses and "is characterized by a single positive-strand genomic RNA known to have a high mutation rate caused by low-fidelity replication and frequent recombination."

"The enterovirus genus comprises the following species: poliovirus, human enterovirus A (HEV-A) (coxackie A viruses and enterovirus 71), HEV-B (coxsackie B viruses, echoviruses, coxsackie A9 virus, and enteroviruses 69 and 73), HEV-C (coxsackie A viruses), HEV-D (enteroviruses 68 and 70), and at least three animal enterovirus species (bovine, simian, and porcine enteroviruses). They all contain a genome of approximately 7,500 bases and positive [(+)]-strand polarity. After infection of the host cell, the genome is translated in a cap-independent manner into a single polyprotein, which is subsequently processed by virus-encoded proteases into the structural capsid proteins and the nonstructural proteins, which are mainly involved in the replication of the virus"

Poliovirus

Incubation period of poliovirus is 1-2 weeks. The prodromal phase shows: Fever, malaise, myalgia (sore muscles), sore throat, vomiting, and constipation. Poliovirus can affect the spinal cord and cause paralysis. In this case, the disease is referred to as poliomyelitis.

Coxsackie and echovirus

Coxsackie viruses (a non-phylogenic group) are mainly associated with human hand, foot and mouth disease.

Echoviruses, on the other hand, are a cause of many of the non-specific viral infections. It is mainly found in the intestine, and can cause nervous disorders.

The usual symptoms of coxackie and echovirus are: Fever, mild rash, mild upper respiratory tract (URT) illness.

Chronic fatigue syndrome

In September 2007, a study published in the Journal of Clinical Pathology reported that acute respiratory or gastrointestinal infections associated with enterovirus may be a factor in chronic fatigue syndrome. The California-based study showed a statistically significant portion of the chronic fatigue study group tested positive for a viral protein compared to the control group.

Enterovirus 71 (EV71)

EV71 was first isolated and characterized from cases of neurological disease in California in 1969. "Enterovirus 71 (EV71), the newest member of Enterovirudae, is notable for its etiological role in epidemics of severe neurological diseases in children. It appears to be emerging as an important virulent neurotropic enterovirus in the upcoming era of poliomyelitis eradication". The illness usually peaks in June or July.

"Enterovirus 71 (EV71) infection may be asymptomatic or may cause diarrhea, rashes, and hand, foot and mouth disease (HFMD). However, EV71 also has the potential to cause severe neurological disease. To date, little is known about the molecular mechanisms of host response to EV71 infection. [...] EV71 infection led to increases in the level of mRNAs encoding chemokines, proteins involved in protein degradation, complement proteins, and proapoptotis proteins."

"Enterovirus 71 (EV71), one of the major causative agents for hand, foot and mouth disease (HFMD), is sometimes associated with severe central nervous system diseases. In 1997, in Malaysia and Japan, and in 1998 in Taiwan, there were HFMD epidemics involving sudden deaths among young children, and EV71 was isolated from the HFMD patients, including the fatal cases. The nucleotide sequences of each EV71 isolate were determined and compared by phylogenetical analysis. EV71 strains from previously reported epidemics belonged to genotype A-1, while those from recent epidemics could be divided into two genotypes, A-2 and B."

Treatment

There is no vaccine or antiviral agent known to be effective in treating or preventing EV71 infection. Experimental vaccines and antiviral agents are being worked on. For example, "both bovine and human lactoferrins were found to be potent inhibitors of EV71 infection"

Malaysia and Singapore

In Malaysia, EV71 outbreaks occurred in 1997 and 2000, mainly associated with genotypes B3 and B4. Since 1997, EV71 epidemics (genotypes B and C) have been reported annually in Singapore, with genotype B4 forming the predominant causative agent of a large outbreak in 2000. In 2008 , the Centre for Health Protection confirmed the total number of infections to 18 so far. In three of the cases, the children infected had traveled to Guangdong and Fujian.

China

From 1999 to 2004, there were no epidemics of hand, foot, and mouth disease in Shenzhen, People's Republic of China, but each year there were small, local outbreaks associated with only a few cases of neurological disease and no reported fatalities. Genetic analysis revealed 19 cases of EV71 among 147 children who had hand, foot, and mouth disease in Shenzhen during this time. As of May 5, 2008, 6,300 were sickened by the viral outbreak which killed another child, in Zhejiang raising the death toll to 26 children, with 1,198 other children affected in that province alone. Specifically, an additional 5,151 cases were reported in Anhui province with scores more in 4 other provinces. 8,531 cases of children infected with hand-foot-mouth disease (HFMD) were reported in China. All the children infected are aged below 6, with most of them being under 2. As of May 7 contagious HFMD led to 28 deaths. Xinhua reported the number of people infected, also rose by 4000 to 15,799. The death toll rose by two to 30, on Thursday, while the number of reported cases jumped to 19,962. It was up by 4 to 34 on Friday, and 43 as of May 16, while reported infections jumped to 24,932.

See also

Other serious illnesses that can arise from these viruses:

• Aseptic meningitis
• Bornholm disease
• Myocarditis/pericarditis
• Neonatal myocarditis
• Herpangina, a painful mouth infection

Sources and notes