Viruses are everywhere
In the soil of the forest, in the dusty air of the city, in the cool water of the ocean, and in your body: viruses are everywhere, they are the most abundant entities on the planet. You are breathing in viruses at this very moment! But most of them just “bounce of” your body and never infect you.
There are plant viruses, human viruses, bacteria viruses, dog viruses, cat viruses, bat viruses… A few of them have made their way into your own genetic blueprint, our DNA, and act as relics of past infections. Those can be reactivated if the right conditions are met.
Not plants, not animals, not bacteria.
At the crossroads of life forms, 1000 times smaller than a millimeter, viruses are one of the driving forces of evolution. By themselves, they lack the ability to reproduce and need a “host” to do so. When this happens, there is an infection. Some viruses will confer a competitive advantage to their hosts, whereas others will kill it. They feel no empathy, fear, or anger. They just exist, and try to spread as much as possible, for that is the hard currency of evolution. Yet, even if some can kill a human being, that is merely a consequence of their hijacking, not a goal.
In a complicated relationship
Human history is full of encounters with these strange genetic entities. The Spanish flu epidemic at the end of the first world war, the HIV epidemic in the 80s, the recent coronavirus epidemic, are all due to viruses. There is even evidence that people got infected with the Hepatitis B virus some 7,000 years ago.
All lot of epidemics are called “zoonoses” and happen when viruses jump from one species to another. A virus is usually restricted to a certain species and infects solely individuals from it. But when individuals from species that did not previously come on contact meet, there is a risk that they start to share their viruses.
Several viruses that caused pandemics in the past are still in circulation. HIV is one of them. In the 80s, it spread massively around the globe and killed millions of people. A zoonosis, it made the leap from primates to humans in Africa through the butchering and consumption of monkeys and chimpanzees. It then became sexually transmittable between humans. Today, the use of antiretrovirals have made this disease nearly a chronic one which can be managed. Many people with well-treated HIV live long lives. Also, there is evidence that resistance to HIV is increasing in people who live in areas with a high prevalence of the virus.
What about now?
So epidemics caused by viruses are nothing new. But several aspects of the current pandemic makes it unique. Firstly, there has never been so many human beings on earth (7.8bn). Secondly, we have never been so interconnected by modern means of transportation before.
The SARS-Cov-2 pandemic is also unique in that everyone is susceptible to infection. There has never been a pandemic of coronavirus before, and thus the immunity in the population as a whole is very low. No country can eradicate the virus in the short to medium term without immense sacrifices. New Zeeland proclaimed itself virus free in May but has seen new cases eventually surge because of tourists or returning citizens. When conquistadores from the old world brought the smallpox to the new world, they themselves had natural immunity to it. But the citizens of the invaded empire of the Aztecs, Incas and the Mayas were susceptible to infection and died by the thousands.
Despite the extensive spread of the current coronavirus, the disease it causes remains relatively benign. Mortality is about 1-2%. Untreated mortality for smallpox of the common type is 30%. The bubonic plague kills 80% of its victims within 8 days. Even if the whole world’s population would get infected by SARS-Cov-2, “only” 156 million people would die and nearly 7,644 billion people would remain. Which means that the world’s population would remain largely unaffected. The black plague of the late middle ages wiped out between 30% to 60% of Europe’s population.
The most probable evolution for the novel coronavirus, after concomitant waves and outbreaks, is that it is going to become less dangerous and cause a harmless cold. Viruses tend to become milder as time goes by, because they coevolve with theirs host, and killing it is obviously not an advantage. But we are still years from this to happen, maybe 5-10 years. It seems like Sars-cov-2 is relatively stable in its genetic code. That means that its capacity to infect and harm its host can be relatively well predicted.
In the meantime, there are two main strategies for dealing with the virus: mitigation and/or elimination. Mitigation involves preventative measures such as social distancing and the development of treatments to reduce mortality. Elimination involves lockdowns and the development of a vaccine to prevent infection. Sweden is a country that is mainly focusing on mitigation and has been doing so from the start of the outbreak. Some countries, like New Zeeland, have been trying to eradicate the virus, to the cost of closing their borders. Most of the countries are trying to contain the virus when infection rates are high (usually above 50 per 100 000 persons), and lower the level of restrictions when infection rates are low.
The development of treatments has been, so far, mildly encouraging. “Repurposing”, or the attempt to use already existing drugs against the virus has shown some promise with the approval of Remdesivir (or “Veklury”, developed for the treatment of Ebola), Dexamethasone (a common steroid) and Heparin (an anticoagulant). Olumiant, a rheumatoid arthritis drug developed by Lilly, is currently being tested in combination with Remdesivir and shows promise. Nonetheless, these so called “emergency approvals” are mainly quite desperate measures to reduce mortality at the early stage of an epidemic . The genuinely interesting, targeted, and effective treatments that are currently being tested are cocktails of novel neutralizing antibodies such as Regeneron’s REGN-COV2.
The end of the pandemic
Typically, pandemics due to viruses end in either two ways: herd immunity is achieved, like for smallpox; or the virus is “controlled” through better treatments and prevention, which is the case for HIV. Herd immunity can be achieved through vaccination or natural immunity, or both.
The way in which a pandemic ends depends mostly on: the mutational behavior of the virus; the price, availability and efficacy of a vaccine and/or treatments; and the political will to eradicate it. The more unstable the genetic material of the virus is, the harder it is to develop a vaccine. For smallpox, eradication of the virus was achieved through a massive international cooperation. HIV is highly unstable, making a vaccine very difficult to make. Influenza strains change in seasonal patterns, which means new vaccines must be designed and produced every new winter season. The efficacy of the influenza vaccine is also relatively low, meaning that it does not confer 100% protection against infection.
How the current coronavirus pandemic is going to end is hard to tell. Since the virus genetic material is relatively stable, vaccines are probably going to be successfully developed. The question remains on how effective they are going to be at protecting patients at risk. Usually, older patients have a weaker immune response to vaccines and since they are most at risk of serious COVID, that might be an issue. The seasonality of the virus is also still debated. If it turns out to be seasonal, new vaccines would need to be designed and produced every year.
There is a need for several different vaccines to get approved, because not one single company has the manufacturing capacity to produce enough doses for the whole world’s population. The sheer size of the distribution needs to eradicate the virus completely will also require an immense international collaboration.
Pandemics in the 6th mass extinction
Even if we are eventually going to control the present virus, one needs to consider the long term prospects of future pandemics. Together with the extensive modification of ecosystems around the globe and the unprecedented loss of biodiversity, the risk for zoonoses has gone up. For instance, humans and bats cohabit more and more at the fringes of tropical forests. But scientists have known for many years now that bats harbor coronaviruses capable of crossing the species boundaries and “jump” to humans. The ongoing destruction of ecosystems shows no signs to stop. Humans encounters with wild animals harboring viruses capable of “making the leap” will likely increase in number, and thus there will undoubtedly be more pandemics. Let us hope that we will be better prepared next time.