Deltacoronavirus

Deltacoronavirus is one of four genera of coronaviruses, which are members of the family Coronaviridae. Different species of deltacoronavirus exist, and most cause enteric disease, or those affecting the digestive system. Along with the species of the other three genera—alphacoronaviruses, betacoronaviruses, and gammacoronaviruses—deltacoronaviruses are single-stranded, positive-stranded RNA viruses. Coronaviruses infect vertebrates, but deltacoronaviruses specifically infect mammals and birds. Some coronaviruses, including some alphacoronaviruses and betacoronaviruses, affect humans, but no outbreaks of deltacoronaviruses have been observed in humans. Deltacoronaviruses have the smallest genomes of all the genera of coronaviruses, though coronaviruses in general have long genomes, which are sets of genetic instructions in a virus or cell.

Overview

Deltacoronaviruses have been found in a wide variety of mammals, including pigs, and birds, though during the first decades of the twenty-first century scientists identified more species that infect birds. However, the presence of deltacoronaviruses and other pathogens in pig populations has drawn some attention from researchers concerned about outbreaks in these populations. Scientists have observed numerous deltacoronaviruses in animals that do not appear to contribute to the development of illness or disease, but a few species of the virus do cause significant illness.

Porcine deltacoronavirus (PDCoV) was first identified in swine in 2009 in Hong Kong. At the time of PDCoV’s discovery, scientists did not find a link between it and any illness the pigs experienced. However, in 2014 scientists identified the virus in piglets in the United States. At that time, scientists identified PDCoV as causing significant diarrhea, vomiting, and dehydration. These symptoms were present among young pigs and usually subsided withing two weeks of infection. Older pigs also contracted the virus, but they seemed to be less likely to get seriously sick from it.

PDCoV can cause major outbreaks of enteric disease, especially in young populations. People sometimes confused PDCoV with porcine epidemic diarrhea virus (PEDV), which is an enteric disease caused by an alphacoronavirus. After studying PDCoV, scientists believe it is related to older deltacoronaviruses found in birds. Research indicates that the PDCoV was most likely in the United States starting no later than 2013. Scientists have identified the virus, which can threaten pork production, in numerous other countries since 2014. In 2022 a group of scientists published the first isolation and whole genome characterization of PDCoV using samples collected from pigs in Peru.

Many deltacoronaviruses are found in birds. Two gamacoronaviruses—turkey coronavirus (TCoV) and infectious bronchitis virus (IBV)—commonly infect agricultural birds. However, deltacoronaviruses have been more commonly identified in wild species of birds. Some species infect specific bird species; for example, bulbul coronavirus HKU11 (BuCoV HKU11) infects bulbuls and thrush coronavirus HKU12 (ThCoV HKU12) infects thrushes. Scientists have also identified deltacoronaviruses in hawks, sparrows, and quail. Researchers have found avian deltacoronaviruses all around the world, but studies suggest they are more common in Asia and might not be established in parts of North America.

Scientists closely study coronaviruses because some that have spread from animal hosts to humans cause serious disease. Scientists have not identified deltacoronaviruses that can infect humans, but they believe it is possible for one to someday mutate and infect humans. Scientists have conducted tests in which they can grow deltacoronaviruses in human tissue, which indicates one of more of these viruses could one day cause an outbreak in humans due to zoonotic transmission.

Bibliography

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