Coronavirus: understanding the enemy

Coronaviriade are a family of RNA virus, therefore their genetic material is ribonucleic acid. Under the microscope, these viruses look like round particles surrounded by projections that reminds the solar corona, and that is why their name.

Coronavirus are known since the 60s, when scientists were studying bronchitis in chickens as well as human viruses from nasal cavities.

Why are viruses so evil?

Viruses are infectious agents that use living cells to replicate. That is, viruses are so simple that they cannot replicate their genetic material themselves and must use cells for this purpose. Clearly, using the cellular machinery from a living organism requires very high specificity. For instance, if you want to drive a car, you need a driving license that won’t be of any use if you want to fly a plane. The same goes for viruses; they must be highly specialized in a particular cell type in order to infect it and use its metabolism. For this reason, there are viruses that infect plants, others infect animals, others infect bacteria…

Because viruses are so dependent on the organism they infect, they don’t usually kill it. If they would, they would as well disappear! In fact, this happens sometimes too. This behavior leads to a Eventually, coevolution occurs between viruses and living beings. That is On the one hand, viruses specialize in a cell type meanwhile and on the other hand, the cell specializes in getting rid of the virus and staying alive. And in most cases, when an organism is infected by a virus, the organism survives. Why is then, sometimes the virulence such, that most infected organism(s) dies? One reason is that the virus is not yet specialized in infecting these individuals and so they haven’t developed adequate defenses to survive it yet.

Additionally, viruses not only specialize themselves in infecting a type of living organism, but also in infecting a specific cell type from it. For example, some viruses infect the immune system and others, the digestive system. Coronavirus infects the respiratory system.


In December 2019, SARS-Co-V-2 (severe acute respiratory syndrome coronavirus 2) was discovered in China. There are still many unknowns about this virus because it a new virus, however, we already know quite a few things already due as well thanks to biomedical research on similar viruses and on this one. It seems that the origin of CoV-2 is animal, and but not human. If we recall the beginning of this article, this means that the virus is specialized on different organisms and, therefore, we haven’t developed a proper immune response against this new virus.

Transmission from human to human occurs through respiratory droplets. i. e. withing the droplets generated in the respiratory system, the viruses travel from one person to another (or some surface) when they he or she sneezes or coughs. If the viruses land on a surface, they are still infectious for hours, and if someone touches the surface and then touches their face, the person could get the virus. Hence the importance of covering your mouth with a handkerchief or tissue when sneezing or coughing, keeping distance from other people if you have a cough, washing your hands well (especially after being on the street) and cleaning objects that you most use (like the cell phone case or the doorknob).

What does the World Health Organization say?

In case of (potential) infection, WHO’s recommendations are avoiding traveling and attending public activities, washing hands with soap, staying home, maintaining good respiratory hygiene, and avoiding touching your face before washing your hands. Using hand sanitizer with at least 60 % alcohol is recommended only when soap and water are not available, because it is not as effective against this virus as soap is.

Why is soap so effective? Coronavirus has a protective hydrophobic lipid bilayer which is dissolved by soap. If the virus loses its lipid protection, it is deactivated and no longer infectious.

Coronavirus, as other viruses, does not affect all population groups equally. There are people more likely to become infected and present severe symptoms due to weak immune system or previous pathologies in their respiratory system. There are also asymptomatic people who can give the infections without even knowing it.

An important aspect to consider is the incubation period of the virus. The longer this period is, the more likely the virus is to spread because infected people aren’t don’t taking the necessary precautions not to infect other people -such as quarantine. The incubation period of coronavirus can be up to 14 days.

Most common symptoms of coronavirus, after the incubation period, are fever (90 %) and dry cough (70 %). Fatigue and expectorate are also frequent symptoms. They are not serious symptoms by themselves, the risk lies in the patient developing can develop pneumonia or other respiratory diseases that, in the worst scenario, might cause their death.

If we analyze death cases in China, people over age 60 are more likely to die, the mortality rate being 3.6 % in the age range 60-69. People between 70-79 have a mortality rate of 8.0 % and people over 79, 14.8 %. Age is not the only risk factor though, but those who suffer from diabetes, hypertension or cardiovascular problems are in higher risk as well.

Fatality rate

The fatality rate of a virus is the proportion of deaths it causes in a given period and in a certain place. To calculate it accurately, it is necessary to know the exact number of infected individuals (E) including asymptomatic cases and to record the number of deaths caused by the disease.

The growth curve of an epidemy depends on the cause of infection. In the case of virus, the previous cases (infected individuals) are the ones that infect and give the virus. Therefore, if there are N cases in a day and an infected individual has been in contact with E people, and being p the probability of being infected, we can estimate the number of people why become infected per day with the following equation:

N = E × p × N

The higher N is, the more cases there will be the next day. That is, the number of infected people will increase every day.

Is it possible to slow down this growth? It is. If E or p is reduced in the equation, the number of infected people every day will decrease. In other words, reducing contact with other people will help reduce the growth factor of the epidemic.

Encouraging news

  • COVID-19 genome is already sequenced, which means that its genes are known and it is easier to develop a vaccine. It would still take a few months to arrive though.
  • We can detect the infection.
  • The situation in China has improve. However, the measures taken has been very drastic.
  • Most cases are mild.
  • Prevention is easy: avoid contact to other people and wash your hands and other objects of frequent use with soap and water.
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