New human coronavirus isolated.

Researchers have isolated a new human coronavirus from a 7-month old Dutch child with bronchiolitis and conjunctivitis (Nature Medicine, published online March 21; doi:10.1038/nm1024).

“We identified a new virus called human coronavirus NL63 (HCoV NL63), which was found in 7% of such patients in our centre in January 2003”, Lia van der Hoekl and Ben Berkhout (Academic Medical Centre, Amsterdam) explained.

Because the virus grows easily in the laboratory, Hoekl and Berkhout believe HCoV-NL63 may also be an attractive model system for testing antiviral drugs. HCoV-NL63 is not as pathogenic as the coronavirus that caused severe acute respiratory syndrome (SARS), but is associated with non-fatal upper and lower-respiratory-tract infection in young children and immunocompromised adults. Like three other known human coronaviruses, its incidence peaks in winter. The team now plans to look at its prevalence in the general population, its association with the common cold in healthy adults, and its replication cycle, which includes identification of the receptor that determines its host cell tropism.

According to Peter Rottier (Utrecht University, Netherlands) detection of the new virus will also help to reduce the unnecessary use of antibiotics. “If SARS does not return in its serious form, this new virus might well become the most significant human coronavirus”, he said.

Luis Enjuanes, of Campus Universidad Autonoma, Madrid, Spain, believes that the newly discovered coronavirus probably will not have a very high impact in terms of human disease. “We already know of two other human coronaviruses that infect human beings on a regular basis without important consequences under normal conditions”, he pointed out.

Christian Drosten (Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany) calls the discovery “doubtlessly remarkable”. However, he added that clarification of the involvement of the virus in other diseases—eg diarrhoea—will also be very important. “Antiviral agents can be sought only now that the virus is known. Promising candidates are beginning to be found for other coronaviruses. These may cross-react with the new one (especially protease inhibitors)”, he commented.

The immune response to the virus also needs to be clarified. “In case the virus is highly prevalent, causes more severe disease, and is efficiently eliminated by the immune system, it may be worthwhile to develop a vaccine. But vaccination for other coronaviruses has proven difficult in animals”, Drosten concluded.