What is behind the flu epidemic in Rio de Janeiro

In recent weeks, the city of Rio de Janeiro has registered more than 23 thousand cases of flu.

The unexpected situation, which is already treated by health authorities as an epidemic, comes at a time when hospitalizations and deaths for Covid-19 are at a low.

Among the factors that help to understand this scenario, experts interviewed by BBC News Brasil highlight the relaxation of restrictive measures against the coronavirus (which, for example, help to prevent infections by influenza, the cause of the flu), the low rate of vaccination against this disease and the large number of vulnerable citizens without immunity against this pathogen.

They also point out that the situation is worrying and it is necessary to take some precautions so that the crisis does not spill over and affect other Brazilian cities over the next few months.

Understand below what is behind this new epidemic in Rio de Janeiro and what can be done to contain it.

the current scenario

Alberto Chebabo, an infectious disease specialist, is in a strategic position to understand the health situation in Rio de Janeiro. He is the medical director of the Clementino Fraga Filho University Hospital, at the Federal University of Rio de Janeiro (UFRJ), and also works at Dasa, a network of laboratories, hospitals and other private health services.

The doctor says that, throughout 2020, Sars-CoV-2 (the coronavirus that causes Covid) reigned practically alone among the respiratory infections that affected Brazilians.

With the advance of vaccination and other preventive care, however, there was an important change in this dispute from the second half of 2021.

Pathogens that were practically gone, such as the respiratory syncytial virus, the bocavirus and the parainfluenza, reappeared and especially affect the health of children, as pointed out in a report published by the BBC in early November.

More recently, it was influenza that showed: Chebabo says that the first case of influenza identified by Dasa in Rio de Janeiro occurred on November 13th.

From there, the growth was vertiginous. “In the week from November 29th to December 3rd, 90% of the samples analyzed by the company registered the presence of influenza H3N2”, reports the infectious disease specialist.

According to the latest figures released by the Municipal Health Department of Rio de Janeiro, more than 23 thousand cases of the disease had already been detected.

The latest InfoGripe Bulletin, published this Thursday (9) by the Oswaldo Cruz Foundation (FioCruz), also draws attention to this new epidemic.

According to the analysis, which takes into account the records of hospitalization for Severe Acute Respiratory Syndrome (SRAG), the increase in influenza infections in the city is already beginning to be reflected in the number of hospitalizations in the state capital.

And there is a risk that the problem will spread elsewhere, warns the bulletin.

“Due to the great importance of the capital of Rio de Janeiro in the national air mobility network, this scenario serves as a warning to other large urban and tourist centers due to the risk of importing influenza cases”, the authors write.

“It is not difficult for this unexpected increase in Rio de Janeiro to be repeated in other cities. It is necessary for city halls to be alert”, agrees Chebabo.

What explains this scenario?

Typically, flu outbreaks and epidemics usually happen between the months of April, May, June and July, at the turn of autumn and winter.

This is because, in the cold season, people tend to be closer to each other and in closed places, which facilitates viral transmission.

The current situation in Rio de Janeiro, which takes place practically in the beginning of summer, is unexpected. Even so, it can be explained by three main factors.

Everything indicates that the H3N2 influenza that travels through Rio de Janeiro was “imported” from the Northern Hemisphere, a region that is now entering the cold season.

“According to the information we have, the strain of influenza circulating in Rio de Janeiro is the same as in Europe and the United States. Possibly someone got infected there and reintroduced the virus in the city”, explains Chebabo.

But for the pathogen to be successful and become a bigger problem here, it needs two conditions: low coverage of vaccination against the flu and lack of adherence to basic preventive measures.

And that’s exactly what he found: with the greater control of Covid-19 in recent months, there has been a drop in the use of masks and social distance, and an increase in circulation on the streets and in the agglomerations. This scenario facilitates the transmission of respiratory viruses, such as Sars-CoV-2 and also influenza.

To top it off, the 2021 flu vaccination campaign was far from achieving its goals. According to the Ministry of Health’s calculations, around 78% of the target audience (which includes children, pregnant women and the elderly) had been vaccinated by September. Ideally, this number exceeds 90%.

Demand was so low that, in July, the federal government announced that the entire Brazilian population could go to health centers to receive a dose of the immunizing agent.

More specifically in Rio de Janeiro, just under 60% of the target audience had been vaccinated against the flu until November.

“Like what happens with Covid-19, flu vaccination is especially important to prevent the most serious cases and complications, which lead to hospitalization and increase the risk of death”, explains public health researcher Leonardo Bastos , from FioCruz.

In other words: there is a huge contingent of people vulnerable to the most serious forms of the infection, even more so because the influenza virus practically did not circulate in 2020.

“This is particularly sensitive in children and young adults, who have not previously been exposed to influenza, especially in the last winter seasons,” says Bastos.

What to do now?

With the flu epidemic in place, the City of Rio de Janeiro resorted to several actions to contain the problem.

The first was the creation of care and testing centers for individuals with flu-like symptoms. Rio de Janeiro authorities have already announced five of these units, which have the capacity to serve 1,000 patients a day.

According to a statement published on the city’s website, this system of care centers “had already been adopted in 2009, during an outbreak of the H1N1 flu. At the time, there was also an increase in demand for care in health facilities.”

Another measure was the reinforcement in vaccination, which came up against the lack of doses and was paralyzed in the first days of December.

The promise is that the campaign will be resumed soon, with the donation of around 400 thousand units of the immunizing agent made by the Butantan Institute, in São Paulo.

Another 100,000 doses, which were transferred from other states by the Ministry of Health, are also on their way to the city.

Immunization against influenza is indicated for the entire population over six months old. The dose, by the way, can be applied on the same day as the vaccine against Covid-19.

“It is also important that other actions, such as cleaning hands, wearing masks and avoiding crowding, continue to happen,” adds Chebabo.

“Another behavior that we need to adopt once and for all is to stay at home, in isolation, when we have flu symptoms such as fever, cough, sneezing and body pain. You shouldn’t work or go to school with these Thus, we reduce the risk of transmitting the virus to other people”, calls the attention of the infectious disease specialist.

And even this package of care, which includes all preventive measures and vaccination, should not be limited to Rio de Janeiro.

“We are talking about a tourist city and with a large movement of people from other cities and states in the country. The epidemic can indeed spread to other places”, reinforces Bastos.

“It’s no use waiting to burst [a epidemia] in your state and only then reinforce the flu vaccination campaign and the necessary care. Even more in this period of the year when we have many agglomerations in shopping centers, public markets and parties”, commented researcher Marcelo Gomes, coordinator of the FioCruz InfoGripe Bulletin, in a series of posts on Twitter.

“Due to the large daily movement of passengers between the main urban centers in the country, especially from Rio de Janeiro, São Paulo and Brasília, infectious diseases, and particularly respiratory viruses, make it very easy to jump from one place to another quickly,” he added.

Although it is less aggressive than Covid-19, the flu is also linked to hospitalizations and deaths.

The World Health Organization estimates that, on the planet, up to 650,000 people die every year from respiratory complications related to the influenza virus.