The COVID-19 pandemic is still very much with the world, as being witnessed by the huge number of cases in China currently and the ongoing number of cases and deaths across the globe. However, the pandemic has shifted to a new and ominous phase, in my opinion.
The virus has transitioned from a global pandemic to a global endemic. In epidemiology an endemic disease is defined as the constant presence of a disease (COVID-19) or an infectious agent (SARS-CoV-2) within a given geographic area or population group. Unfortunately for human kind, both the disease COVID-19 and the viral agent causing the disease SARS-CoV-2 have become a constant presence throughout the world, thus an endemic global disease problem, not unlike influenza, but more lethal. How did this happen and what can we do about it to protect ourselves and future generations for many years to come?
While the origin of the SARS-CoV-2 virus is still being debated, it does appear from the perspective of many scientists that the virus originated in nature and spread to humans from an animal, most likely a bat, either directly or through a secondary host like a Civet cat sold for human consumption. This is known as a zoonotic disease, one spread from animals to humans. This is how the initial SARS-CoV-1 virus spread to humans in 2003. Regardless of the origin of the SARS-CoV-2 virus, the reality is that it has become widely distributed within both the human population as well as domestic and wild animals across the globe.
One might ask, why did not the SARS-CoV-1 virus in 2003 become so wide spread and how was that disease stopped in 2004? There are three factors that helped to end that outbreak before it became a pandemic. First, there was no asymptomatic or pre-symptomatic transmission of the virus from person to person, as is the case with SARS-CoV-2. As a result, contacts of those found to have SARS-1 were able to be identified and quarantined to prevent further spread. Secondly, the virus was less contagious than SARS-CoV-2. And third, luck had it that most cases were identified in locations such as Toronto and Hong Kong, which had strong public health systems in place to control the spread of the virus. We were not so lucky with SARS-CoV-2. As a result, the SARS-CoV-2 virus was allowed to spread widely to humans in almost every place on Earth, and as I will discuss, to both domestic and wild animals across the globe as well
In his excellent book, “Breathless,” David Quammen describes the rapid and wide spread of the SARS-CoV-2 virus among as host of both domestic and wild animals in many diverse locations across the globe. The first was a dog in Hong Kong in February 2020, then cats in China, France, Belgium, Italy, Rusia, Germany, New York, Texas and Minnesota. These animals contracted the virus from humans, however there is also evidence of animal to human transmission. The other problem is that cats will be able to transmit the virus to house and deer mice, which will then spread it to other mice in the wild. Since deer mice represent the most abundant non-human mammals in North America, the virus will be present in these animals for the foreseeable future. (2) The SARS-CoV-2 virus has also been found in various zoo animals including tigers, lions, snow leopards, gorillas, hippopotamuses, white tail deer and minks.
Mink and white tail deer infection with SARS-CoV-2 has been of particular concern here in the United States and in Europe. The SARS-CoV-2 virus has spread widely to white tail deer in America. Sampling of deer in Iowa found a positivity rate of 82.5%, and 31% in New York State, 44% in Pennsylvania and 67% in Michigan. The United States has a white tail deer population of over 25 million. As Quammen describes, U.S. Department of Agriculture Officials found that wild mink in Utah tested positive for the SARS-CoV-2 virus, and the viral sequence from those wild mink matched the virus in mink from a nearby mink farm. “This raised the prospect of SARS-CoC-2 gone rogue into the American landscape. In the lingo of disease ecologists: a sylvatic cycle.”
Basically, a sylvatic cycle means that once a virus is widespread in wildlife, it will spread to humans and non-wild domestic animals. As a result, pathogen transmission then involves spread from domestic animals to other domestic animals and to humans, and human to human, referred to as the urban cycle. This is exactly where we are now with regard to the SARS-CoV-2 virus. There is no herd immunity where there is a sylvatic cycle, the virus will always find a susceptible human from an animal and begin the cycle of human-to-human spread, as the virus continues to evolve and mutate in the wildlife population. Considering the level of infection already among the wildlife population, as Quammen states, “then there is no end to COVID-19.”
So where does that leave us and what can we do to protect ourselves going forward? First, we must recognize that COVID-19 is here and will be with us at some level for many years to come. We will continue to witness surges of disease with many hospitalizations and deaths, especially among those with underlying health issues and the unimmunized. The virus will continue to evolve and mutate both in humans and animals, resulting in the potential of a lack of immunity from previous infection and prior immunizations. Secondly, we still need to take precautions to prevent infection, such as wearing masks in indoor spaces with many people, washing hands, and getting additional booster vaccines as they become available and indicated. Anyone currently not vaccinated should get vaccinated as soon as possible. Third, research into better treatments for those infected and ill with COVID-19. Fourth, increased global surveillance to quickly identify new variants of the SARS-CoV-2 virus so that new vaccines can quickly be developed to protect against the new variant. Lastly, as is being done with influenza, research into developing a universal coronavirus vaccine that would protect us from any new variant.
We have made remarkable progress in helping to control the COVID-19 pandemic, but the threat is still very much with us, and will continue to be a threat for many years to come. As we move into this endemic phase of this disease, we all have a responsibility to take the necessary steps to protect ourselves and our community. The virus will continue to do what viruses do to survive and spread. It is up to us to make their job much harder and less destructive.
Rich DiPentima of Portsmouth spent more than 30 years as a public health official and epidemiologist, including service as deputy public health director in Manchester and chief of communicable disease epidemiology at the New Hampshire Division of Public Health.