Brazil’s Fiocruz to test flu vaccine against new H3N2 variant

RIO DE JANEIRO, BRAZIL – In addition to the considerable number of cases, the flu epidemic in Rio de Janeiro has a worrisome component. Among the variants of the influenza virus circulating in the city, there is a recent mutation of the H3N2 that had not yet been identified in Brazil.

The variant is provisionally named H3N2 Darwin, because it was first reported in the city of Darwin, Australia. “It is a mutation of the virus circulating in the Northern Hemisphere that has reached Brazil,” says virologist Fernando Motta of the Laboratory of Respiratory Viruses and Measles of the Oswaldo Cruz Institute (IOC/Fiocruz), among the researchers who identified the mutation in Brazil.

He says the laboratory has isolated the strain and is now preparing to conduct tests to assess whether the current flu vaccine used in Brazil works against the strain. “I believe we will have this answer in two weeks,” Fernando says. The flu vaccine is updated annually, but since the strain is new, it is unclear if the vaccine used this year will work to prevent infections.

It is also unclear if the strain is predominant in Rio de Janeiro at this time due to a limited number of genetically sequenced samples of the virus. Therefore, it is impossible to say that the H3N2 Darwin is more transmissible than the other influenza strains.

UNTIMELY EPIDEMIC

Infectologist Ana Helena Germoglio explains that the H3N2 is a known virus and there are several subtypes within it. “The last influenza vaccine contained the Hong Kong subtype, but not the Darwin subtype,” the specialist says. University of Brasilia (UnB) virologist Bergmann Ribeiro believes that nevertheless, immunizers probably have some effect against the new subtype. “The vaccines should be efficient against this current virus,” he says.

Outbreaks and epidemics of the flu virus are not unprecedented, but they draw the experts’ attention due to the time of the year: usually, cases occur during winter. Bergmann believes that the current high number of cases, at the beginning of summer, may have been caused by the decrease in mask use and the return of events and crowds.

The infectologist explains that the influenza vaccine does not offer long-lasting protection, and is effective for about 6 months – that is why the national immunization campaign runs between March and April, just before the normal peak in cases. “The problem is that we were caught by surprise, the virus came at an unexpected time,” the doctor says.

IINFLUENZA VS COVID-19

The symptoms of the respiratory syndrome caused by the Influenza virus are very similar to those of Covid-19 (fever, body aches, fatigue, throat inflammation, runny nose and cough). In most patients, the symptoms of the disease subside in about 7 days, and the lethality is considered low, between 0.1% and 0.2%. In contrast, the probability of death from Covid-19 is between 1% and 2%.

“When we compare influenza with Covid-19, the coronavirus causes more severe cases. But when we look at mild cases, the symptoms of influenza are more pronounced. The H3N2 Darwin is not potentially more dangerous, but we don’t have immunity to it, and that’s why there are more people infected this season,” Ana Helena explains.

To prevent infection, the precautions are the same as for Sars-CoV-2: washing hands, keeping a physical distance, avoiding crowds, and wearing a mask. At any sign of symptoms, testing is recommended to differentiate infections and to stay home to avoid transmitting the virus.

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