Chikungunya cases trigger and light the alert of a new epidemic in Brazil

According to the latest epidemiological bulletin published by the Ministry of Health, cases of chikungunya increased by 31% in Brazil compared between 2020 and 2021.

Until December 4 of this year, 93,400 probable cases of the disease, caused by a virus and transmitted by the bite of the Aedes aegypti mosquito, had been registered.

The Northeast region continues to be the most affected, with an incidence of 111.7 cases per 100,000 inhabitants. But the increase of affected people in other parts of the country is also noteworthy, such as the Southeast, which reported 29.1 cases per 100,000 individuals.

In São Paulo alone, the number of people affected by chikungunya jumped from 281 in 2020 to 18.2 thousand in 2021, which represents an increase of more than 6,000%.

By way of comparison, the other two diseases that also depend on the action of this same mosquito had a drop: the number of patients with dengue fell 45.7%, while that of Zika dropped by 15.4% in the same period analyzed.

Among the possible explanations for this difference, experts interviewed by BBC News Brasil highlight the less intense way in which chikungunya has spread throughout Brazilian territory since it was introduced here, in 2014, in addition to the huge number of susceptible people in various regions of the country .

They also fear that the arrival of summer and warmer days will represent an even greater rise in cases of the disease over the next few weeks.

“Viruses transmitted by Aedes they have a seasonal characteristic, and there is an increase in the frequency of cases during the rainy and hot seasons, which usually provide a favorable environment for the proliferation of these mosquitoes”, explains Dr. Melissa Falcão, from the Brazilian Society of Infectology.

“We therefore expect an increase in chikungunya cases in the coming months”, he adds.

A disease where sequelae are the rule, not the exception.

Doctors usually divide chikungunya into three phases.

The first is acute, which lasts up to ten days and is usually marked by fever, fatigue and body aches.

Then comes the subacute phase, which lasts for up to three months. In it, fever is no longer a concern, but the pain can intensify and affect mainly the joints of the hands, feet, ankles and knees.

Finally, more than half of those affected progress to the chronic phase, which is also marked by discomfort in the body’s joints.

“Researches carried out in India, which also presents many cases of chikungunya, show that this chronic phase can persist in some patients for up to five years”, calculates virologist Rômulo Neris, doctor in immunology and researcher at the Federal University of Rio de Janeiro (UFRJ). ).

And this, of course, represents a torment for the individuals themselves and for the entire health system.

“During outbreaks, the impact of chikungunya is very large. The units are overcrowded, with an increase in demand for assistance in more than 100% in the emergency care units”, says Falcão.

“And a chikungunya epidemic now could have even more negative impacts, as we’ve got healthcare professionals fed up with the backbreaking work of the Covid-19 pandemic,” he adds.

As you may have noticed from the last few paragraphs, pain is the main complication of the disease. Her own name, by the way, comes from Maconde, one of the languages ​​spoken in Tanzania, where the first epidemic was registered in the year 1953.

In this language, the word chikungunya refers to “twirl” or “bend over”, in direct reference to the severe discomforts that affect the joints and muscles and make patients shrunken and prostrate.

And although the disease has been known for a few decades, all the mechanisms behind so much pain months or even years after the viral invasion are still not known.

“In some individuals, we even found a residual infection in the tissue surrounding the joints. In others, we didn’t see any more viruses,” says Neris.

“It is possible that this picture has something to do with the response of the patient’s immune system, which ends up getting deregulated and harming the body itself”, speculates the specialist.

But what explains this new increase now?

A resident of Feira de Santana, Bahia, infectious diseases specialist Melissa Falcão closely followed the first wave of chikungunya that swept a large part of the country in 2014.

“This virus was introduced in Brazil simultaneously in two cities: Feira de Santana (BA) and Oiapoque, in Amapá”, he recalls.

In 2016 and 2017, large outbreaks of chikungunya were recorded in Pernambuco, Paraíba and Ceará.

“But, unlike what we observed with dengue and Zika, the spread of this third disease across the country occurred heterogeneously. It spread quickly throughout the Northeast, but had a slower spread than expected in other regions”, he analyzes.

Falcão recalls that Brazil experienced a strong dengue epidemic between 2015 and 2019, which makes many people have a high immunity against this disease now. Something similar happened with Zika as well: the very rapid and wide spread of the disease across the country from 2015 onwards has reduced the number of susceptibles more recently.

From a physician’s point of view, this difference in epidemiological scenarios helps to understand why the two diseases (Zika and dengue) underwent a reduction in 2021, while chikungunya had a recent increase in cases, as there are still a large number of Brazilians susceptible to this third infection.

It is worth noting that the increase in the number of patients is taking place in the Northeast, but it is also beginning to advance in other places.

“Cases of chikungunya have been increasing in regions that were previously spared, such as the State of São Paulo, which has faced, since the beginning of 2021, the first most important transmission of this disease”, he points out.

Falcão observes that, in São Paulo, the Baixada Santista region accumulates around 97% of registered cases and that this shows “a potential for the spread of the disease to other regions”.

Neris adds other possible factors that help to understand the current scenario.

“We also need to consider the wide distribution of Aedes mosquitoes by Brazilian cities and a possible increase in the capacity of testing and diagnosing this disease in recent years”, lists the virologist.

“Furthermore, we also need further studies to verify that the chikungunya virus has not mutated or acquired an ability to transmit itself more easily. This possibility for now is just speculation, but it also needs to be investigated,” he adds.

What to do now?

In the experts’ view, there are at least four major strategic axes that could be strengthened to contain cases of chikungunya in the coming months.

“The Federal Government needs to further increase its testing and surveillance capacity, monitor individuals with suspected infection and offer treatment according to the symptoms”, says Neris.

BBC News Brasil contacted the Ministry of Health to obtain a position regarding the increase in cases of chikungunya and what measures are being taken, but no responses have been sent until the publication of this report.

“States and municipalities, on the other hand, must reinforce measures to control the vector of the disease, the Aedes mosquito. This involves the application of larvicides and insecticides, the creation of task forces to eliminate breeding sites and the work of health agents, who beat the house of people to pass on the prevention guidelines”, points out the virologist.

Science also has a lot to contribute with new solutions against chikungunya, such as vaccines and antiviral treatments. Unfortunately, research in this area is slow: according to the ClinicalTrials.Gov website, which gathers information on clinical trials with new products, there are only seven active studies that look for an immunizer against this disease.

By way of comparison, there are currently 534 researches on vaccines against Covid-19.

“In this sense, a field that has advanced a lot is the inoculation of the Wolbacchia bacteria into Aedes aegypti. When present inside this mosquito, this microorganism prevents dengue, Zika, chikungunya and urban yellow fever viruses from developing, contributing to the reduction of these diseases”, points out Falcão.

Research evaluating this strategy is ongoing (including in Brazil) and has brought promising results in recent months.

Finally, there is individual responsibility for preventing chikungunya and other diseases transmitted by Aedes.

“It is worth making use of repellent, which is effective to prevent mosquito bites, which are usually more active in the early morning and late afternoon”, suggests the infectologist.

“The population also contributes by eliminating mosquito outbreaks in homes. It is enough to check once a week all the places where there is accumulation of standing water, which serves as a breeding site”, he advises.

Among the possible deposits, it is important to check from large objects, such as swimming pools and uncovered water tanks, to tighter spaces, such as cans, pet bottle caps, plant vases and the liquid reservoirs of the refrigerator and air conditioning.