“Whether our predictions hold true or not remains to be seen in the future. But we think it’s highly likely, given what we know so far, COVID-19 will eventually become seasonal, like other coronaviruses.” - Dr. Hassan Zaraket, Virologist, American University of Beirut
“An optimist understands that life can be a bumpy road, but at least it is leading somewhere. They learn from mistakes and failures, and are not afraid to fail again.”
- Harvey Mackay, American businessman and author
Vaccinating every eligible person on planet Earth—ASAP—is the top priority in conquering SARS-CoV-2, the coronavirus that causes COVID-19. On February 16th, President Joe Biden stated that every American who wants a vaccine is going to be able to get one by the end of July 2021. And while the vaccine rollout in many countries remains problematic, by February 20th 199 million doses had already been administered in 87 different countries (60.5 million in the United States).
We are beginning to see the light at the end of the tunnel. Not only are we are getting closer and closer to achieving herd immunity but we are also getting much closer to understanding what the end game for SARS-CoV-2 may look like. Many experts posit that the most likely scenario is that SARS-CoV-2, just like four of its coronavirus cousins, will lose its virulence and become one of the many viruses that cause seasonal upper respiratory tract infections (URIs), aka, “the common cold.” In this Germ Gem post, I explain that while SARS-CoV-2 is here to stay, ultimately it is expected to go from public enemy number one to merely a seasonal nuisance.
Brief overview of coronavirus infections. The coronaviruses are a large group of RNA viruses that commonly infect birds and mammals. As we’ve seen with SARS-CoV-2, they undergo frequent mutations, yielding new variants that can cross species barriers, that is, they can be transmitted from one type of animal to another.
Since 1960, seven types of coronaviruses have been identified that cause infections in humans: NL63, 229E, 0C43, HKU1, SARS-CoV-1, MERS-CoV, and SARS-CoV-2. The first four of these coronaviruses were identified in the latter half of the 20th Century and are responsible for 15-30% of the annual (seasonal) URIs, that is, the “common cold.” On average, adults contract two to three colds per year. As a rule, colds are relatively mild illnesses manifest by cough, sore throat, runny nose, and low-grade fever.
But the last three newcomers—coronaviruses that emerged in this century—are all notable for generating much greater havoc. SARS-CoV-1 caused the relatively short-lived (2003-2004) pandemic of severe acute respiratory syndrome (SARS). Like its closest cousin SARS-CoV-2, SARS-CoV-1 originated in China. The original source of both of these coronaviruses appears to be the Chinese horseshoe bat. (Civet cats served as a reservoir host—meaning a host that serves as a source of infection and potential reinfection—of SARS-CoV-1; the reservoir species of SARS-CoV-2 is yet to be identified.) MERS-CoV, the cause of Middle East Respiratory Syndrome (MERS), emerged in Saudi Arabia in 2012. While its origin isn’t fully understood, bats are implicated as the source, and dromedary camels are a reservoir host. To date more than 2,500 cases of MERS have been identified in 27 countries. The case fatality rate (CFR)s of SARS and MERS, 11% and 37.1%, respectively, are much higher than that of COVID-19 (estimated between 0.4% and 3.4%), which in turn are all higher than the CFR of seasonal influenza (0.1%).
Seasonal viral URIs. Viruses love the human upper respiratory tract. Many of them circulate in seasonal epidemics. Their circulation in some tropical regions is, however, constant, that is, they are endemic. The rhinoviruses, the most common viruses that cause URIs, plague us mainly in the spring, summer, and early fall. Influenza and respiratory syncytial virus infections are most common in the fall and winter (in the Northern hemisphere). Enteroviruses circulate in summer and early fall. Adenoviruses make their appearance in late winter and early spring. The four coronaviruses mentioned above (NL63, 229E, OC43 and HKU1) that cause URIs, surface in winter and spring. (Some researchers speculate that at its start OC43 may have been more virulent and responsible for the “Russian flu” pandemic of 1890.)
It is hard for us to imagine that SARS-CoV-2, which in its first year as a human pathogen killed almost 2 million people worldwide, is going to simmer down and join the ranks of seasonal URIs. The case that COVID-19 is here to stay and will become a seasonal virus was argued in the September 2020 issue of Frontiers in Public Health in a review entitled “Seasonality of Respiratory Viral Infections: Will COVID-19 Follow Suit.” Nonetheless, most experts warn that until herd immunity is reached by a combination of natural infections and vaccinations, SARS-CoV-2 is likely to continue to cause waves of COVID-19.
SARS-CoV-2 won’t go away. Only two viruses have ever been eradicated from our planet and both were achieved through heroic vaccination programs. In 1980, variola major, the cause of smallpox, was declared eradicated, which was a cause for major celebration as discussed in my September 23, 2020 Germ Gems post. In 2011, a paramyxovirus that caused rhinderpest, a highly contagious disease in cattle, was eradicated. Most experts believe, however, that SARS-CoV-2 can’t be eradicated; it won’t go away.
In the case of smallpox, variola major was not a zoonotic infection; it had no animal reservoir. Thus, once the smallpox vaccinations eradicated the virus from Homo sapiens, it was banished from the planet. In contrast, the three modern day coronaviruses mentioned above are all zoonotic infections, that is, they can be transmitted from animals to humans. And they can exist indefinitely in animal reservoirs.
It was recognized early in the COVID-19 pandemic that SARS-CoV-2 can also be spread from humans to nonhuman animals causing what is called an anthroponosis. Not only can SARS-CoV-2 be transmitted from infected humans to cats (including tigers) and dogs, but rodents are at risk. In the past several months huge, economically devastating COVID-19 outbreaks occurred in mink farms in Denmark, The Netherlands, and most recently, in Taylor County, Wisconsin.
In a February 19th New York Times article, David Quammen, an expert on transmission of pathogens between species and author of the highly acclaimed Spillover: Animal Infections and the Next Human Pandemic, reported that two gorillas in the San Diego Zoo Safari Park had contracted COVID-19, presumably from a zookeeper. Underscoring the important role of non-human animals in COVID-19, he suggests, “Five years from now, when much of the world’s population will have been vaccinated against Covid-19 but maybe a billion people won’t, either for lack of opportunity or by stubborn refusal, the virus will still be with us. It will circulate among the unvaccinated, sometimes inconspicuously, sometimes causing severe illness or death, and it could also abide among wildlife populations, mutating and evolving in ways no one could predict. If it crosses back from them to us, it may ignite new outbreaks, start us coughing again and even bring with it some ugly genomic innovations.”
On February 16, 2021, Nature published a survey of more than 100 immunologists, virologists and infectious disease researchers entitled: “The coronavirus is here to stay—here’s what it means.” According to this survey, all of us need to get used to living with SARS-CoV-2. But the good news is that over time, this virus is likely to pose much less danger to Homo sapiens. In fact, a large majority of these researchers thought it is very likely that while SARS-CoV-2 won’t be completely eliminated from any region of the world, it will become endemic. Moreover, the consensus was that once herd immunity is achieved, COVID-19 will behave like one of the seasonal viral URIs. While most of these experts expressed confidence that our immune system has lots of tricks up its sleeve, they’re also aware of the ongoing mutations of SARS-CoV-2. They agreed that over time our immunity will probably wane thereby requiring new vaccines and/or adjustments to current vaccines. Indeed, maintaining a certain level of immunity may be key to keeping the virulence of SARS-CoV-2 in check.
Keep your guard up. Vaccinations against COVID-19 are the key to ending this pandemic. I am therefore concerned with some of the comments I hear from people saying they will not get vaccinated because the current vaccines may not provide lasting immunity and that they may have to get an additional vaccine or an adjustment to the vaccines currently available. To all of these people, I say, “Do your part: get vaccinated.”
None of us should be alarmed by the fact that after completing our initial COVID-19 vaccinations, we may need additional inoculations to maintain our immunity against this deadly virus. This should be nothing new to any of us. Throughout our lives, we’ve maintained our immunity to certain viruses by getting booster shots or additional inoculations. In fact, annual vaccinations are “par for the course” against influenza virus to cover new mutations, and older adults should receive a vaccine to rearm the immune system against varicella zoster, the virus that causes chickenpox and “shingles.”
And, immunizations aren’t just for children. Depending on your age, job, life style or health conditions, you may be at risk for other vaccine-preventable diseases and need to be immunized. The Centers for Disease Control and Prevention’s website provides a list of continuously updated science-based recommendations for immunizations of adults. Check it out! Follow its recommendations! I do.
My wife and I eagerly await SARS-CoV-2’s completion of its journey along the long and bumpy road to finally join the ranks of the common cold viruses. In the meantime, we qualified for and received our second COVID-19 jabs last week. We experienced no side effects, other than a sense of relief. Finally, we can look forward to a “new normalcy” and begin planning to get together with our children, grandkids, and friends.
