2020 has gone down in history as the year of the COVID-19 pandemic. Little could we imagine, at Christmas 2019, that in a few months an unknown virus was going to force half the world to be confined, causing an unprecedented global health, social and economic crisis in the 21st century.
During this time, the world’s leading research teams have worked tirelessly to find out as much as possible about SARS-CoV-2 and the infection it causes, and during the month of December several countries began the first vaccination campaigns. There is still much to discover and know, but 2021 begins with a little more light. What do we know so far? The Carlos III Health Institute has just published a very complete report that compiles all the scientific evidence available up to the date of its preparation, in the last fortnight of 2020.
For more details, we recommend reading the report in its entirety, although here we summarize some of the information it contains:
Origin and biology of the virus
The exact origin of SARS-CoV-2 has not yet been revealed, but it is known that transmission to people came from an animal, perhaps directly from a bat or through infection of an intermediate species, as occurs in SARS and the MERS.
Thanks to genomic sequencing using patient samples from various geographic areas, it is possible to trace the spread and evolution of SARS-CoV-2, which, like all viruses, undergoes various mutations as it spreads. It is currently known that SARS-CoV-2 does not overmutate, but given its pandemic nature, it is necessary to closely monitor the emergence of new variants, such as the one recently described in the United Kingdom, since they can alter the evolution, extension or severity of the pandemic.
How is the virus transmitted?
The routes of contagion are similar to those described for other coronaviruses, mainly the secretions of infected people that are transmitted by air. Transmission by means of aerosols that can remain suspended in the air also seems important, so it is recommended to avoid closed spaces and to ventilate adequately. The infection can also be transmitted by contact with objects contaminated with these secretions.
Diagnostic methods
The most reliable test is PCR (polymerase chain reaction), which consists of the amplification of the genetic material of the virus and which has a high sensitivity and specificity.
Somewhat less sensitive are antigen tests, popularized in recent months, but which can be reliable in people with symptoms and during the first 5-7 days.
Serological tests are also available, which allow detecting antibodies against the coronavirus with a blood sample; that is, they give information about whether a person has already passed the infection. These types of tests are useful as a research tool and for doing seroprevalence studies.
Clinical manifestations and immune response
Although many people can transmit the infection by being asymptomatic, those who do develop any signs of the disease may have a cough, sore throat, fever, loss of smell, loss of taste, headache, shortness of breath, and diarrhea.
The big problem is that not all people develop all symptoms: they can appear in isolation and with different intensity . This, together with the large number of asymptomatic patients, makes it very difficult to control the spread of the virus.
SARS-CoV-2 can also potentially affect other organs and in the most severe cases presents various clinical manifestations such as lung infection, pneumonia, kidney failure, vascular pathology, etc.
Normally the immune system is able to control the virus before it spreads through the body, preventing it from reaching the lungs. In the case of SARS-CoV-2, the so-called interferon system offers an effective response in the early stages of infection. In a second phase, the specific immunity mechanisms – antibodies and lymphocytes – are set in motion, generating a very powerful and specific response against the virus, which manages to control the infection in most cases.
epidemiology
SARS-CoV-2 coronavirus infection does not affect everyone equally. Generally speaking, older people tend to suffer from a more serious disease, with a higher probability of complications; It has also been proven that COVID-19 affects men more than women, and that the infection is milder in children and young people.
The seroprevalence study carried out in Spain, the ENE-COVID, has just published the preliminary results of its fourth round and indicates that around 10% of the Spanish population would have been infected since the start of the pandemic. In Spain, the lethality of the virus is around 1%.
Treatments and vaccines
No specific treatment for COVID-19 is yet available. Corticosteroids are the only drugs that seem to have shown some usefulness in reducing mortality in critically ill patients, although their efficacy is still under investigation. Experience with antiviral drugs previously used in other pathologies has not shown positive results and much scientific evidence is still lacking.
Yes, there has been more success in the case of the vaccine: there are currently ten prototypes that have already entered or completed phase III trials. The first to achieve approval from regulatory agencies have been RNA vaccines from the companies Pfizer-Biontech and Moderna.
You can read the full report, prepared by the scientific journalist José A. Plaza, here.
