Enteroviruses: Tiny but versatile pathogens

The genus ‘Enterovirus’[1] belongs to the family Picornaviridae (‘pico’ meaning small) which comprises of icosahedral viruses (~30 nm in diameter) with single-stranded, positive-sense RNA genomes. As of 2020 (http://taxonomy.cvr.gla.ac.uk/PDF/Picornaviridae.pdf), the family contained 63 genera and 147 species, with many others still awaiting classification. Enteroviruses may cause subclinical infections of humans and animals or potentially fatal diseases of the heart, gut, liver, and the central nervous system. Among the major genera of the genus are Echovirus[2], Coxsackievirus types A and B[3] Poliovirus and Hepatovirus (the cause of hepatitis A is the only member of this genus).  

Enteroviruses are also associated with occasional outbreaks. For example, Echovirus-11 has been incriminated   in 2023 in an outbreak of severe neonatal infections in France and elsewhere.

Enteroviruses can also cause pandemics. Such an event occurred in the early 1980s with over 80 million clinical cases of conjunctivitis (eye infection) mostly in the coastal tropical regions of the globe with fomites and hands as the major suspected vehicles. The virus was also found to survive better on fomites under conditions of high relative humidity.

Specific antiviral therapy for enteroviruses infections is still under development with the treatment focussing on preventing complications. The same is true for vaccination against enteroviruses. However, a notable exception here is the highly successful vaccination against poliomyelitis. The combined use of the injectable Salk vaccine and the oral Sabin vaccine has been remarkably successful in the virtual eradication of polio. The anticipated eradication of that disease will be only the second example (after smallpox) of how medical science will have wiped off a dreaded infection!

CREM Co Labs has facilities for and experience in working with many types of enteroviruses to study the virucidal activity of environmental surface disinfectants and hand hygiene agents. However, the Public Health Agency of Canada now restricts the storage and use of the vaccine strains of polioviruses to Containment (Biosafety) Level 3 (CL-3) facilities and that too only under special cases (https://www.canada.ca/en/public-health/services/laboratory-biosafety-biosecurity/roles-progress-poliovirus-containment.html). Canada is among the first countries to do so in respect of the embargo issued by the World Health Organization.    

Further reading:

1) Alexander E. Gorbalenya, Tapani Hovi, Nick J. Knowles et al.: Virus Taxonomy

The ICTV Report on Virus Classification and Taxon Nomenclature Picornaviridae Chapter. 2020 Sep.

 2) Zell et al.: ICTV Virus Taxonomy Profile: Picornaviridae. Journal of General Virology, 2017; 98: 2421–2422.

3) Sattar SA, et al.: Spread of acute hemorrhagic conjunctivitis due to enterovirus-70: effect of air temperature and relative humidity on virus survival on fomites. J Med Virol, 1988 Jul;25(3):289-96. doi: 10.1002/jmv.1890250306).

4) WHO report: Enterovirus-Echovirus 11 Infection – the European Region. 2023 Jul.

5) Marc T, Nigel C: Enterovirus infections in neonates. Semin Fetal Neonatal Med, 2009 Aug; 14(4):222-7. doi: 10.1016/j.siny.2009.02.002. Epub 2009 Mar 19. PMID: 19303380 Review

6) Li C , Wang H, Shih Sh,  Chen T, Li M: The efficacy of viral capsid inhibitors in human enterovirus infection and associated diseases. Curr Med Chem, 2007;14(8):847-56. doi: 10.2174/092986707780363032.

7)  Nikonov O S ,  Chernykh E S,  Garber M B,  Nikonova E Yu: Enteroviruses: Classification, Diseases They Cause, and Approaches to Development of Antiviral Drugs). Biochemistry (Mosc). 2017; Dec;82(13):1615-1631. doi:10.1134/S0006297917130041.

[1] This term is not to be confused with ‘enteric viruses’, which includes a wider variety of non-enteroviruses (e.g. rotaviruses) often found causing infections in the gut or the enteric cavity.

[2] Named ‘enteric cytopathogenic human orphans’ in the mistaken and outdated belief that these viruses were in search of a disease.

[3] Named after the town Coxsackie, New York, where they were first discovered.