The COVID-19 pandemic marks the third novel coronavirus outbreak in the 21st century.
Unlike the viruses that cause Severe Acute Respiratory Syndrome and Respiratory Syndrome in the Middle East that have been associated with limited outbreaks, SARS-CoV-2 – the virus that causes COVID-19 – burned in just over two Months since the first worldwide The case was reported last December in Wuhan, China.
Most countries, including the United States, soon began to grapple with the public health crisis.
On March 11, the World Health Organization officially declared COVID-19 a pandemic. At the time, the WHO said that more than 118,000 human cases of coronavirus had been reported in 114 countries and nearly 4,300 people died.
“We are deeply concerned about the alarming spread and severity and alarming inaction,” said Tedros Adhanom, WHO Director General.
“We have never seen a pandemic caused by a coronavirus.”
Coronavirus
Coronaviruses are a large family of viruses found in dogs, cats, horses, cattle, pigs, chickens, turkeys, humans, and bats. Several bat coronaviruses have been shown to be zoonotic pathogens, and man-made diseases range from a mild cold to severe pneumonia with the potential to be fatal.
“It is important to realize that there are a number of coronaviruses that have been infecting people for decades. These viruses often make up 10 to 20% of all colds in humans, ”said Dr. Christopher W. Olsen, Professor Emeritus of Public Health in the University of Wisconsin-Madison School of Veterinary Medicine and the School of Medicine and Public Health.
For reasons unknown, neither SARS nor MERS were as highly infectious and adapted to human-to-human transmission as the COVID-19 virus.
Linda Saif, PhD, professor and coronavirus researcher at Ohio State University College of Veterinary Medicine
Dr. Olsen spent much of his career studying zoonotic infections and was an advisor to the Centers for Disease Control and Prevention During the SARS Epidemic. Coronaviruses are not generally getting any more deadly for people, Dr. Olsen. Rather, the viruses that cause SARS, MERS and COVID-19 are each novel coronaviruses to which people have no immunity and to which they are fully susceptible.
While the SARS and MERS viruses are more deadly than the COVID-19 virus, neither are as infectious as this newest novel coronavirus, according to Linda Saif, PhD, professor and coronavirus researcher at Ohio State University’s College of Veterinary Medicine.
The death rate from SARS and MERS was 10% and 34%, respectively, explained Dr. Saif. The estimated death rate for COVID-19 ranges from less than 1% up to 3.4%. “For reasons unknown, neither SARS nor MERS were as highly contagious and adapted for human-to-human transmission as the COVID-19 virus,” she said.
“As RNA viruses with their ability to recombine and acquire mutations, coronaviruses are more likely to develop and gain the ability to transmit between species, much like influenza viruses,” continued Dr. Saif continued. “This is partly why we are seeing more coronaviruses causing these pandemics.”
A likely explanation for the origin of the COVID-19 virus is that it is a recombinant coronavirus that is naturally produced from a bat coronavirus and another coronavirus in an intermediate animal host, explained Dr. Saif. Pangolins were originally thought to be this host, but viral sequencing showed it likely isn’t, she said.
Viral hosts
Bats are as diverse as the viruses they carry.
With more than 1,300 bat species around the world, bats are the second largest order of mammals after rodents.
Researchers have studied bat behavior, eating habits, migration patterns and echolocalization. Few early studies looked at bats as hosts for viruses beyond the rabies virus.
That changed with the 2003 SARS epidemic, which was ultimately linked to bats. Since then, more than 120 viruses have been identified in different bat species, including several novel coronaviruses as well as the Ebola, Hendra and Nipah viruses.
Today, bats are increasingly considered to be one of the most important animal reservoirs for newly emerging infectious viruses.
One of the ways in which a bat could have infected a person directly with COVID-19 is that a person could eat the bat in soup, for example, or come into contact with bat droppings or secretions at the exotic animal markets that are common in China, said Dr. Saif. Similarly, bat droppings are sometimes sold in stores for use in traditional Chinese medicine, she said, adding that fruit or other foods contaminated with bat droppings or urine could be a foodborne route of transmission to humans.
Deja vu again
The veterinary epidemiologist Dr. Donald Noah isn’t surprised that a novel zoonotic virus is responsible for the current pandemic.
“Something like this would happen and it will happen again,” said Dr. Noah, associate professor of public health and epidemiology at Lincoln Memorial University College of Veterinary Medicine.
Prior to his academic career, Dr. Noah held senior positions at the Department of Defense and the Department of Homeland Security, where he served as Assistant Assistant Secretary for Biological Defense Against Weapons of Mass Destruction. As Deputy Deputy Minister of Defense, Dr. Noah part of the government’s response to the 2009-10 swine flu pandemic, or H1N1 influenza, which killed around 12,000 Americans.
“Even after the COVID-19 pandemic is over, we will not be able to literally or figuratively wash our hands off it,” said Dr. Noah. The continued expansion of the human population to include wildlife habits, he explained, means more human-animal interactions that make exposure to a new zoonotic disease more likely.
Dr. Noah is reluctant to use the phrase “silver lining” about an ongoing pandemic, but hopes Congress will be forced to proactively prevent these public health crises before they begin enacting health laws.
“Zoonotic pathogens do not perceive any species differences. They don’t perceive geographic boundaries, ”he said. “The problem is that disease monitoring and response systems are separated between humans, veterinarians and the environment.
“Federal agencies have no choice but to pool their efforts against these pathogens. The alternative is to continue to accept the uncontrolled occurrence of disease. “
“There is not much we can do about disease emergence,” concluded Dr. Noah, “but we can be better prepared to respond faster, more effectively, and more collaboratively to minimize loss of life and economic difficulties.” . ”
Reverse zoonoses
Dr. Saif said veterinarians should be involved in all aspects of zoonotic infections, along with a one-health approach.
“Veterinarians need to be part of identifying the animal reservoirs and intermediate hosts for these diseases,” she said. “This could focus on wildlife medicine, such as understanding the habitat and diversity of bat species as a reservoir for coronaviruses and several other viruses.”
Even after the COVID-19 pandemic is over, we cannot literally or figuratively wash our hands.
Dr. Donald Noah, veterinary epidemiologist and former Assistant Assistant Secretary for Biological Defense Against Weapons of Mass Destruction, Department of Homeland Security
In addition, studies of bat physiology and immunity are vital to understanding how bats are, according to Dr. Saif can harbor so many viruses without disease.
“A similar focus is needed for avian influenza transmitting birds and pigs as influenza hosts,” she said. “The question of which factors influence the transmission between species is unknown.
“Also, more veterinarians should work with other researchers to develop the most appropriate animal models for these diseases, as we cannot test antiviral drugs or vaccines without an animal model that reproduces human diseases and responses.”
Regarding whether a pet can get infected with the COVID-19 virus from a sick owner, Dr. Saif states that researchers want to investigate this. The Centers for Disease Control and Prevention has indicated that there is no evidence that pets get sick, nor is there any evidence that dogs or cats could be a source of infection with SARS-CoV-2, including the Spread of COVID-19 to humans. AVMA has developed a number of FAQs that cover this topic.
“Veterinarians should be at the forefront of this research to see if a new disease can cause reverse zoonosis and spread from humans to pets and farm animals,” she said.
