Two completely different viral outbreaks are making international headlines and originating in China – one affects people and one affects pigs. They share the similarity of being viruses, but that’s where it ends. The 2019 Novel Coronavirus (2019-nCoV) and African swine fever (ASF) are very different.
And experts agree that these viruses are not linked.
“What is clear about 2019 Novel Coronavirus is that is has nothing to do with African swine fever,” says ASF expert Dan Rock, professor of pathobiology at the University of Illinois. “These viruses are very distinct from one another – they are not closely related at all.”
Breaking Down Coronaviruses
The two viruses are completely different in terms of their basic structure and genome, the tissues in which they replicate and the diseases that they cause, says coronavirus (CoV) expert Linda Saif, Distinguished University Professor in the Food Animal Health Research Program at The Ohio State University.
Unlike ASF which has a DNA genome, CoV has an RNA genome which allows the virus to mutate and change very similar to influenza viruses. Saif says this is how CoV acquires the ability to infect different tissues and to infect different species of animals.
“For many years, coronaviruses have been circulating in humans that cause only mild disease like the common cold,” she says. “In fact, most coronaviruses are not deadly, especially in healthy adults. Most healthy adults and adult animals recover from coronavirus infections.”
How Do Coronaviruses Affect Animals?
In 1995, Saif’s laboratory was the first to document the interspecies transmission of coronaviruses from wild ruminants to cattle and from cattle to poultry. In cattle, her team documented that respiratory CoV infections frequently occur in animals shortly after periods of stress such as arrival to feedlots following long-distance shipping, and they identified them as a component of the shipping fever complex.
Stress and co-infections can make CoV infections more severe. Saif’s team also showed that the respiratory strain of porcine CoV is generally a mild infection in swine, but when coupled with co-infection with other viruses like porcine reproductive and respiratory syndrome virus (PRRSV), it can be more severe.
Most animal coronaviruses infect the intestinal or respiratory tracts and cause diarrhea or respiratory disease. Saif says the best examples of CoV that infect the gut and cause diarrhea and deaths in pigs are porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus that first emerged in the U.S. in 2013-14. Both are still present in pigs.
These viruses are members of two different groups of coronaviruses – alpha and delta CoV. Saif explains they are genetically distinct and do not cross-protect against one another. 2019-nCoV is part of a third distinct group of coronaviruses (beta CoV) and is genetically and antigenically distinct from these two swine coronaviruses, she adds.
“The 2019-nCoV is most closely related in the coronavirus family tree, like a first cousin of the SARS CoV that infected humans in China in 2002-03 and was from a bat origin,” Saif explains. “The 2019-nCoV is also thought to be a descendant of a bat CoV but there may be other animal hosts, most likely another wild animal that was in the seafood and wild animal market in Wuhan China where the 2019-nCoV originated.”
Could 2019-nCoV Impact the Swine Industry?
There is no evidence from China that 2019-nCoV came from pigs or even that it could infect pigs, Saif says. In addition, there was no previous data that the related SARS CoV infected pigs.
Coronaviruses have the ability to jump species from time to time under the right circumstances, Rock says. Experts believe this likely happened with 2019-nCoV. Humans were exposed under the right circumstances to become infected.
“A unique feature of this group of coronaviruses is that they appear to be a little more promiscuous with the host they use or can infect,” Rock adds.
What Can We Do?
There are no antivirals for 2019-nCoV, but Rock believes the knowledge gained from SARS of the rapid identification of that virus and its propagation in cell culture, indicates vaccines and antiviral treatments for 2019-nCoV could be more rapidly developed than before. This possibility is supported by similar statements made by Anthony Fauci, M.D., Director of the National Institute of Allergy and Infectious Diseases, NIH.
“I am not as concerned about Novel Coronavirus as some of the media are. Time will tell how serious a matter it actually is,” Rock says. “I believe this epidemic will subside and the push for a vaccine will drop off.”
However, when it comes to ASF, Rock says the fact that the ASF virus is now endemic in China’s pig herd poses a major threat to the U.S. swine industry because it’s out and about. From his perspective, that’s the big question – how does the swine industry manage and deal with that virus?
“Now, as at all times, it is important to be vigilant and maintain high levels of biosecurity for swine herds,” Saif says. “But this is especially critical in an effort to keep out ASF, a more severe and deadly infection than CoV, because it infects all age groups, not just the young. ASF is even more stable, more transmissible and harder to eradicate once introduced.”
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