Will COVID-19 become an endemic disease?
With SARS-COV-2, some cases of reinfection have been documented. However, it is not yet known with certainty how common these reinfections are and in what period they occur
Much is still unknown about COVID-19 and the virus that causes it, SARS-COV-2. But, other infections in the past have shown that it is very likely that this coronavirus will continue to be transmitted, even if one or more vaccines appear.
A BBC Mundo report addresses the issue of whether this disease — which has affected almost 45 million people in the world and has almost 1.2 million fatalities — will become a disease that will be sustained over time or will finally be able to be controlled.
In that sense, the question is whether this virus will be one of the long list of pathogens that cause “endemic infections” in the human population, those that continue to be present in a geographic region or circulate routinely in specific months of the year.
Scientists currently view the COVID-19 virus as an “epidemic” because it continues to spread rapidly. But when is an infection considered endemic?
“An endemic virus is part of the ‘landscape’, a disease that recurs, regularly or continually recurs in an area”, explained Jeffrey Shaman, professor of environmental health sciences at the Mailman School of Public Health at Columbia University in New York. , in an interview with the BBC.
“For example, malaria is an endemic infection in sub-Saharan Africa. West Nile virus is endemic in the United States. Dengue is endemic in much of Central and South America. Influenza, whose nature is highly seasonal, is also considered endemic because we have not managed to control it”.
Endemic potential of COVID-19
Shaman published a study in the journal Science exploring the potential for SARS-COV-2 to become endemic. In research, the professor identifies the crucial factors that cause a pathogen to establish itself in a population.
“The main factor that has an impact on endemicity is how long the immunity of an infected person lasts. Also, if this person is susceptible to reinfection due to decreased immunity”, explained Shaman.
He adds that “it is still not known with certainty how long the immunity of this coronavirus lasts. But, based on the coronaviruses that already exist and that infect the population regularly, such as those that cause colds, we know that people get these viruses again and again”.
Indeed, previous studies show that a person can be infected with the same coronavirus up to three times in a year.
With SARS-COV-2, some cases of reinfection have been documented. However, it is not yet known with certainty how common these reinfections are and in what period they occur.
Precisely, the latter is a characteristic that must be determined so as to know if the coronavirus will have the capacity to become endemic. However, there are other factors that will also have an impact on the endemic potential of SARS-COV-2.
Vaccine effectiveness
Among the elements that can define whether COVID-19 will be endemic is the emergence of vaccines. Now, can humanity have a really effective vaccine that offers protection for long periods?
“If we manage to develop a vaccine that generates a robust and persistent response, we will be able to prevent people from getting infected. This way, we will prevent the virus from becoming endemic”, Shaman told BBC Mundo.
“This could be something similar to what happens with the measles vaccine. This disease is highly contagious, but the vaccine is very effective and has managed to reduce the number of infections ”, added Shaman.
“We have outbreaks in communities and the measles virus is still latent. However, it does not have the capacity for sustained transmission and it is not an endemic virus”, explained Shaman. He also warned that another scenario could occur in which a “partially effective” vaccine is achieved.
An example of this is the influenza vaccines that currently exist. They offer partial protection against viruses and must be updated every year.
Also, since not all people are vaccinated, there is sufficient susceptibility in the population and the influenza virus continues to spread.
What about the ‘endemic regions’?
Something that is observed in this pandemic is how certain regions and countries have many problems to reduce the levels of infection. In many cases, these are areas that combine high levels of poverty, overcrowding, labor informality and little access to health systems, explained the BBC.
A study by the UK Public Health Office addressed the reality of some disadvantaged communities. In those areas, lockdowns have little impact in reducing infections. Therefore, there, the COVID-19 virus “could be firmly established” and “could be endemic”.
The same is true in some regions of Latin America, where there is a link between the highest concentrations of COVID-19 cases and the highest levels of poverty, overcrowding and labor informality.
So, could this lead to the possibility of COVID-19 “endemic regions” in the future? This is currently the case with malaria and HIV, endemic virus in parts of Africa. There is also the case of dengue, which is endemic in Latin America.
“The answer is yes”, highlights the researcher from Columbia University. “This is a huge concern in certain parts of the developing world”, he adds.
Inequalities: A huge challenge
For Shaman, “it is clear that this virus has raised the health inequalities that exist in the developed world. It is also seen how the virus disproportionately impacts the poorest communities and minorities. An example of the latter is lived in the United States”.
All these inequalities — says the researcher — will be a huge challenge to reduce the levels of infection. Failing to do so, will have an impact on the virus’ ability to become endemic.
So if SARS-COV-2 becomes endemic, can the infection be managed, for example, as is now done with influenza?
“That is one possibility. However, we still have a lot of uncertainty, such as the question of immunity and whether reinfections will be less and less severe”, says Shaman.
The report adds that what happened with the influenza pandemic of 1918 could be repeated. That time, there were three waves of infection, until the disease became a variant of seasonal influenza.
At the same time, he adds that a scenario like the one that occurs with dengue, a virus whose infections are more severe with each reinfection, could also be seen.
The COVID-19 virus will continue to circulate
Shaman explains that the only certainty is that the virus will continue to circulate. Furthermore, SARS-COV-2 is very likely to establish itself as a pattern of endemicity. “There are many possibilities because eradication is very unlikely”, says the researcher.
Finally, he maintains that they hope to achieve “levels of infection that are controllable and that the virus will be less and less severe. In this way, there will be a balance in which the endemicity of this pathogen is not so bad for the majority”.
“That would be the kind of stability that would allow us to live with this virus and, at the same time, return to the old normality”, he said.
