COVID-19: What we still don't know

It's amazing what we have learned about COVID-19. When the pandemic started, the coronavirus behind the disease was completely unknown to humanity. Only a few viruses related to it were known remotely. This was one of the reasons that we were so ill-prepared to face what began in early 2020. However, in less than a year we have learned almost everything there is to know about the virus. How it infects cells including the target proteins it binds to and the molecular mechanism it employs or the possible mutations and the consequences of each on the lethality of the virus are just some of the most amazing things we have learned. In fact, just a few months ago some of these, such as the effect of mutations in the virus genome on its lethality, were on the list of unknowns. As of today, although we do not know exactly what will happen, we have quite reliable forecasts with which we hope to be prepared. This kind of knowledge would have been difficult for us to obtain or impossible just twenty or thirty years ago. We know a lot about the virus, for example: the symptoms it causes, how to diagnose it and what we can expect from it, but we still have a lot to know.

The scientific community is reluctant to state the type of airborne transmission of the virus. Despite the measures taken and the moderate evidence in this regard, the exact route of transmission is unclear. Contact with contaminated surfaces has been ruled out as the main source of contagion. Aerosols, which remain suspended in the air for hours, have not been totally ruled out. While the direct transmission by the drops that are produced when speaking, coughing or sneezing have been demonstrated as a source of contagion.

The mortality of the disease does not reach a scientific consensus either. Although it seems that it should be easy to establish the fatality rate, there is great variability between age groups, populations or even neighborhoods. That is why a standardized fatality rate for everyone has not yet been made official. We know that older people with obesity or diabetes, hypertension, or coronary heart disease are more prone to severe disease. However, we still do not know how it is that young and healthy people fall to the disease randomly. Similarly, symptoms can be very diverse in magnitude. While some people have only exhaustion, headache, and fever, others must be hospitalized. A clear relationship has not yet been established between the amount of virus with which it is infected, nor between other parameters and why it affects so much some people and not others.

One of the great unknowns associated with the COVID-19 disease is the long-term sequelae caused by the disease. It is obvious that we still cannot know exactly what will happen to the patients who manage to recover and it is that we had never faced this disease yet. The most serious patients, who can spend up to 3 months in intensive care, recover slowly. The numbers of recovered are around 20 million, but doctors are observing that many of them show In many cases the sequelae of total immobility or sore throats after being intubated for two months are those that we already know. Others, such as anosmia (which we have already discussed here) are typical of viral infections. But we do not know the damage to heart or lung tissue that the disease leaves behind. Wounds can heal but tissue is not 100% functional again. We still have to see if after passing the disease, patients are more likely to catch the flu, a common cold or to catch COVID-19 again. Similarly, we don't know for sure whether the flu and the common cold generate some immunity against COVID-19, although current data seem to indicate that they do.

On the other hand, we have the vaccines that are being developed around the world. A lot of media pressure and hope is being put into a process that we really don't know will work. The effectiveness of vaccines is tested during their generation, but we will only know their long-term effectiveness as time goes by. We cannot ensure that the vaccine will be effective with just one dose in a lifetime. Annual campaigns may have to be carried out to vaccinate the entire population until a vaccine is found that will make the immune system react forever. Although it is also possible that like the flu, it is impossible to find an effective vaccine from one year to the next.

Thanks to the enormous monitoring effort, it is the first time in history that the spread of a disease can be traced. This has shown that there are a large number of asymptomatic patients. Epidemiologists do not know very well why this high percentage is due, or if it occurs in other infections. The truth is that we are learning a lot about epidemics and infections, which will surely make us react better and faster when an episode like this comes again.

Bibliografía:

Jiao Gong, Jingyi Ou, Xueping Qiu, Yusheng Jie, Yaqiong Chen, Lianxiong Yuan, Jing Cao, Mingkai Tan, Wenxiong Xu, Fang Zheng, Yaling Shi, Bo Hu. A Tool to Early Predict Severe 2019-Novel Coronavirus Pneumonia (COVID-19) : A Multicenter Study using the Risk Nomogram in Wuhan and Guangdong, China. MedRxiv Mar. 2020.

del Rio C, Collins LF, Malani P. Long-term Health Consequences of COVID-19. JAMA. Oct. 2020.

Scientific Brief: Transmission of SARS-CoV-2: implications for infection prevention precautions. World Health Organitation. Jul 2020.

COVID Human genetic Effort. https://www.covidhge.com/

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