The first 6 months of the COVID-19 pandemic have accumulated close to 5.5 million confirmed cases and close to 350,000 deaths in the world.
Spain has been one of the countries hardest hit by the first wave of the tsunami. More than two months after the alert status was declared (March 14) and the confinement was ordered, nearly 300,000 cases and 29,000 deaths have been confirmed. Being high figures, they are an underestimate of the real number, since diagnostic tests have not been performed in many suspected cases.
Since prevention measures have included the suspension of most jobs and business activities, the economic urgency to return to normalcy is increasingly pressing for many families and governments.
Can there be immune people?
In this situation it is imperative to know how many people have been infected. And, above all, to know if that gives them protective immunity. But what do we know about it?
Antibody tests allow you to know who has been infected and who has not. They are different from PCR tests, which diagnose active cases, that is, people who at that moment replicate the virus and are contagious. Generally this period does not go beyond 10 days. It is known as ‘3 + 7 rule’, that is, contagiousness 3 days before symptoms and 7 days after onset. During this period, those infected can transmit the virus to others. Once cured, almost all patients develop antibodies.
The experience with other human coronaviruses is that HIV-positive people are protected, at least for a time (2-3 years), and they no longer infect anyone. To confirm if the same happens with SARS-CoV-2, a study recently published in the journal Science has examined the degree of protection against the new coronavirus in macaques. And there is good news: it concludes that the initial infection elicits antibodies that are neutralizing and protect against a second exposure to the virus.
Therefore, there is no fear of reinfection and there is reasonable hope for an immunoprotective vaccine.
Antibody frequency in the population
The results of the first antibody studies show disparate results in different parts of the world. In the state of New York, where the pandemic has been intense, a study of more than 3,000 citizens has registered antibody rates of 14% in the population, being up to 21% in Manhattan and even higher in the Bronx.
We also have data from California, on the other coast of the United States: the antibody rate in Los Angeles was 4.6%.
In Europe, the estimation of infected people has been done in different ways. In France, infection rates of 4.4% have been reported, although in Paris they are 10%. In Spain, the government has released the preliminary results of the ENE-COVID-19 study, which has examined the presence of antibodies in more than 60,000 people distributed throughout the country. The global prevalence has been 5%, although in large cities such as Madrid it exceeds 11%.
Although the seroprevalence data for the new coronavirus show significant variations from one place to another, even within the same country, we can conclude that the majority of the population has not yet been infected. In other words, you are susceptible to illness if exposed to the coronavirus.
Intelligently de-escalate
COVID-19 is first and foremost a health crisis. Of course there will be economic and social consequences, but it is not a question of choosing between prolonging the confinement to save more lives or returning to normality to save the economy. After all, we must not forget that poverty and mortality also go hand in hand.
We must recover the activity and, at the same time, protect the most vulnerable. Let us remember that the fatalities of COVID-19 have been in more than 75% of the cases people over 75 years old, many of them in geriatric residences. For the rest of the population, mortality from COVID-19 is less than 0.5%.
Although it is necessary to return to work as soon as possible, we must do it with new habits. Remember that the size of the viral inoculum is probably the main determinant of infectivity and, to a large extent, also severity of COVID-19. It seems that up to 80% of infections have been produced by only 10% of those infected. If there is social distancing and activities in open spaces, the transmission rates (R0) will fall below 2, so that a group immunity (‘herd’) below 50% will suffice to control the epidemic.
Quick isolation of new diagnostics
A group of German experts concluded a few days ago that an “adaptive containment” strategy may be the best way to deal with the immediate future. They pointed out three priorities:
Consolidate hygiene measures;
Expand diagnostic tests;
Isolate infected early and quarantine contacts.
There is a translation of the document from German to Spanish.
Given that the new coronavirus replicates in the oral cavity and there are high concentrations of viruses and antibodies (IgG and IgA) in saliva, it seems a priority to develop diagnostic tests in saliva. They must be rapid tests, which provide results in 10-15 minutes and can be repeated periodically, especially if there has been a risk exposure or suspicious symptoms appear.
Finally, these tests should be cheap and sold in pharmacies, such as those for pregnancy or HIV.
Vicente Soriano, Faculty of Health Sciences & Medical Center, UNIR – International University of La Rioja
This article was originally published on The Conversation. Read the original.
