By : Mina Al Akko
With the global rise in the number of COVID-19 cases, one expects a corresponding rise in the number of deaths. However, many health care providers are reporting that the virus’s lethality is waning. “In March and April, patients reached the emergency room very sick. They had acute respiratory distress syndrome, multi-organ failure. They needed immediate oxygen, ventilation, and in two to three days, we had patients that died” says Matteo Bassetti, the director of the Infectious Diseases Clinic at the San Martino Hospital in Genoa, “but now, in the past four to five weeks, it’s been totally different. Patients of a similar age as the ones before, even very elderly patients, are not as sick as patients were just four to six weeks before”
COVID-19 is an RNA virus that causes respiratory infections in humans. Like any other virus, COVID-19 cannot survive outside of its host. It infects its host to make more copies of itself, since viruses lack the proper machinery that could be utilized for this purpose. Having an RNA genetic map makes the virus more likely to make errors when making copies of itself, because the machinery used to copy its genetic material is error-prone and prioritizes speed at the expense of accuracy. Such a trade-off results in an extremely high mutation rate, most of these mutations are deadly to the virus, but some are beneficial. The virus with the beneficial variation is more likely to survive and make more copies of itself, becoming the most populous version of its type. In this context, the virus that does not kill its host quickly is the one that is more able to survive and propagate. Why is this the case?
The inception of COVID-19 was accompanied by a higher death rate. This high lethality of the virus might seem like an advantage, but this is far from the truth. As described earlier, viruses are not able to survive independently. They also need enough time to be transmitted from one person to another. The virus’s high lethality leads to the host’s early death, and the virus would not have an opportunity to be transmitted to another host. Consequently, the virus dies as well. This concept is known as the Red Queen Hypothesis. The Red Queen is a character from Lewis Carroll’s Through the Looking Glass. The novel describes how the Red Queen has to run faster and faster in order to remain in the same place. This makes an evolutionary sense. Both populations of the pathogen and the host must evolve as fast as they can merely to stay alive. If a version of the virus out-evolved its host in a way that leads to the host’s swift death, that virus and its progeny will perish as soon as the host dies.
It is tricky to conclude that the potential decrease in COVID-19’s lethality is due to its ‘weakening,’ since numerous variables have to be taken into account. One of which could be the weather. However, one thing is for sure: COVID-19, and all viruses alike, do not want to kill their hosts before they have had an opportunity to infect another host. The good news is, our immune system is fighting as hard as it can to hinder the virus from triumphing at this arms race.