There are still many unknowns about the new coronavirus, SARS-CoV-2, which causes covid-19, the new viral disease that is progressing rapidly in several regions of the world and which has also touched Portugal – after countless suspected cases without confirmation, this Monday, in Porto, the first two patients were confirmed.
Fighting the new epidemic more effectively will depend on new knowledge about the virus, about which the mysteries remain. Scientists are in a race against time to study SARS-CoV-2 and learn more about the contours of the disease it causes. This alone will allow the development of an effective vaccine and medicines that help to fight covid-19 and control the epidemic, which now appears to be striding towards a pandemic situation.
Here are the main unknowns about the new coronavirus that is spreading in the world.
What is the origin of SARS-CoV-2?
In fact, it is not known. What is known is that it emerged in December, in China, in a market in the city of Wuhan, where live animals were traded. The coronavirus is zoonotic, that is, it originates in an animal, and it has crossed the species barrier, starting to infect humans. However, it is unknown what its original reservoir is, as well as the intermediate animal that facilitated the jump of the species barrier.
Scientists think that the original reservoir of the virus could be bats, similar to what happened to the coronavirus that caused the SARS epidemic in 2002 and 2003. However, bats were not sold on the Wuhan market and, on the other hand, there is no laboratory (genetic) confirmation that this is the case.
A study by a group of Chinese researchers, who compared genetic sequences from SARS-cov-2 with coronavirus resident in pangolins, pointed the finger at this endangered mammal as the intermediary for human infection. But to date, these data have not been confirmed by any other research group.
On the one hand, the information provided by the Chinese team did not concern the entire genome of the coronavirus (of which there is already a preliminary version), only a specific genetic sequence. On the other hand, comparisons made by other groups in relation to this small genetic sequence of SARS-cov-2 and pangolin coronavirus did not find genetic coincidences greater than 91%.
To be sure, the genetic coincidence would have to be greater than that, explains Arinjay Banerjee, a coronavirus researcher at McMaster’s Canadian University, cited in Nature.
In the case of the coronavirus that caused SARS, says the same specialist, the genetic coincidence with the coronavirus found in civets, a species of wild cat that in this case facilitated the passage of the species barrier, was 99.8%.
On this front, the search continues and there are still more questions than answers.
How is the virus transmitted between people?
Here, too, there are more questions than definitive answers. It is already known that the disease is not only contagious after the first symptoms appear, because there are confirmed cases of contagion on the part of patients who are still asymptomatic, but it is not known whether this always occurs, or only in a part of the cases.
As with other respiratory diseases, available data suggest that the virus spreads through droplets of saliva released by patients’ coughing and sneezing, but that does not seem to be the only way.
Studies have detected the presence of viruses on surfaces and objects, which seems to indicate that contagion will also be caused by contact with these contaminated surfaces. Even though there is no certainty, the recommendations therefore emphasize the need for frequent hand washing.
It is also unknown at this time whether there could be sexual contagion, either through feces and urine, or whether after curing, a person can continue to transmit the disease, or even become ill again. All of these issues are still open, and that does not help in the fight against the epidemic.
What is the mortality rate of covid-19?
There is still a great deal of uncertainty about this, especially since we may still be seeing only the top of the pyramid at this point, as experts say. In other words, many cases of infection may be going unnoticed, as they do not cause serious symptoms and are not even tested – and confirmed – in the laboratory.
The largest study to date on the epidemic, which covered a total of 44,672 confirmed cases and was carried out by the Center for Disease Control and Prevention in China, found a mortality rate of 2.3%, corresponding to a total of 1023 deaths, in the group of more than 44 thousand patients – the seasonal flu mortality rate is less than that.
But this is just an average. The same study indicates that in people over 80 years of age the mortality rate rises to 14.8%. The existence of chronic diseases and a compromised immune system help to explain this greater lethality in older age groups.
Still according to the same study, the overwhelming majority of cases (80.9%) do not go beyond a mild infection, while 13.8% of patients have a severe infection and 4.7% evolve to a critical situation.
According to the WHO, covid-19 is less deadly than SARS or MERS, the other two known acute respiratory infections, caused by other coronaviruses, which are a kind of cousins of the new coronavirus. The SARS mortality rate was 10% and that of MERS was between 20% and 40%. But, unlike the new virus, which is very easily transmitted, those two were less contagious.
Experts believe that the death rate of covid-19 may still decrease, as the real numbers of the epidemic are known.
Why does this disease seem to hardly affect children?
There is no answer to this question. It is not known whether children have mostly benign infections, which have gone unnoticed, or whether they are simply not very sensitive to infection with this new coronavirus. If so, it is more of a mystery to unravel.
When can there be a vaccine?
At this time, several experimental vaccines are under development, but the first clinical trials of some of them are not expected to begin before April. This will undoubtedly be the most effective way to fight the disease, since it allows to prevent its emergence, but experts and the World Health Organization (WHO) estimate that a vaccine for Covid-19 will not be available before one year.
In some of these future vaccines, however, researchers are trying to speed things up, using procedures that allow you to walk faster: instead of developing huge amounts of virus (for the vaccine), which would take more time, the process goes on for using mRNA (the messenger RNA), the genetic material that derives from DNA and contains information for the production of proteins – in this case, coronavirus proteins.
This product is then injected into the patient’s body, and the cells of the immune system are expected to become familiar with the brand of the virus and trigger an immune response when they are present – that is, after all, the principle of the vaccine.
So far, this type of vaccine has not been very effective in other cases. It remains to be seen whether it may be different in relation to the new coronavirus.
Are there any specific medications for the new coronavirus already?
No. The treatment for now available is just what attacks the symptoms. But a huge effort is underway to test drugs already approved for other viral diseases, in order to verify if they can have any beneficial effect in the treatment of covid-19. Medicines already approved for clinical practice have the great advantage of not having to go through the time-consuming phase of safety tests for human use. If any of the drugs being tested show effectiveness, they may also start to be used in these patients.
At this time, according to Nature, there are more than 80 clinical trials underway in China regarding potential treatments for the new viral pneumonia. In testing are, in particular, drugs used against HIV and Ebola viruses. An antiviral called remdesivir is also being tested, which was developed to fight infections by two other coronaviruses, which caused the SARS epidemic in 2002 and 2003, and which caused MERS in 2012, and which showed encouraging treatment results of the infections caused by them.
The preliminary results of some of these clinical trials will be known over the next few weeks.
Could the arrival of hot weather help stem the epidemic?
It is not known. Other viruses that cause respiratory diseases are seasonal, becoming less active with the arrival of heat. But this is a new virus and it is not known how it will behave in this regard.
Can the virus be eradicated, or is it here to stay?
This is yet another unanswered question. If the virus is here to stay, and if it behaves like others that cause seasonal respiratory infections, then this clash with the human population, being the first, will also tend to be the most serious. This is if, as with influenza viruses, for example, the infection gives immunity to those who have been infected. But this too is still unknown.
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