Off-season flu spike in São Paulo sounds alarm for the rest of the country

Major pediatric hospitals in São Paulo, Brazil’s biggest city, have seen sharp increases in flu cases outside the virus’s traditional contagion season. Child facilities such as Sabará, Darcy Vargas, and Cândido Fontoura report 20-percent increases in care for youngsters with flu symptoms over the last few weeks.

Hospitals had expected influenza cases to increase in June and July, a standard pattern at the height of Brazil’s winter. However, hikes in patient numbers were moderate, with Covid infections still dominant.

Now, as Brazil enters its first day of spring, the increase in laboratory tests positive for Influenza A is increasing among pediatric units, with researchers talking about a “broken pattern” of the virus’s seasonality.

The country saw another off-season spike in H3N2 at the end of last year, as Covid protection measures began to be lifted nationwide. The barrier that masks and social distancing had created allowed the flu virus to spread quickly around the country.

The timing of this latest hike worries experts, as the oscillating temperatures at the beginning of spring generally lead to an increase in respiratory infections — which could be made worse by a flu spike.

A potential aggravating factor is the city’s low level of flu vaccination. Coverage in São Paulo stands at just 55 percent, far below the 90-percent target.

Brazilian health experts are always sure to take note of infection curves in São Paulo, as the transit of people in and out of the megacity can cause outbreaks to spread quickly nationwide — as was the case during the Covid pandemic.

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