Manaus is the largest city and capital of the Brazilian state of Amazonas, in the vast Amazon rainforest. After being hit hard by the outbreak in April and May – with cemeteries reportedly struggling to dig graves fast enough to bury the dead – deaths have dropped dramatically in the city.

A scientific study posted on the website medRxiv suggested that Manaus may have reached herd immunity, the point at which enough people have antibodies to the virus that it slows or stops the spread. Scientists estimated that up to 66% of the population there had antibodies to Covid-19.

“All signs indicate that it was the very fact of being so exposed to the virus that brought about the reduction in the number of new cases and deaths in Manaus,” the study’s co-ordinator was quoted as saying.

But now cases are once more on the rise. After reopening quickly, authorities on Friday banned gatherings and parties for 30 days and restricted opening hours for shops and restaurants.

Mayor Arthur Virgilio told Reuters news agency that President Jair Bolsonaro was to blame. “The government must take this seriously and speak the truth,” he said.

Critics of the president accused him of downplayed the risks of the virus throughout the pandemic, ignoring expert advice on social distancing and other measures.