The uptick comes exactly a year after the Zika virus – another mosquito-borne disease – was declared a global health emergency, and as during the previous epidemic Brazilian authorities are struggling to calibrate an appropriate response.

Because there is a vaccine, yellow fever should, in theory, not cause as much of a panic but global vaccine stocks are dwindling, and the disease is far more deadly than Zika.

Of the 107 confirmed cases in the state of Minas Gerais, 40 ended in death. Three patients have also died in São Paulo state and one in Espírito Santo.

Although the disease has a more than 200-year history in Brazil, concern has picked up steadily in recent months as it moved to areas of the south-east, such as Espírito Santo, where it is not normally found.

As a precaution, the health ministry has expanded production of vaccines and administered 3.3m doses in Minas Gerais, where the outbreak is concentrated.

So far, it has been spread by Haemagogus and Sabethes mosquitoes in rural areas.

Monkeys have also suffered. More than 400 were found dead in Espírito Santo after farmers reported an unusual silence in the forest. Biologists warn that endangered species, such as the muriqui, could be wiped out as the vaccination only works on humans

Pedro Tauil, an epidemiologist at the University of Brasília, said the latest spread of yellow fever was different from the past both in terms of the number of cases and the range.

“Seeing cases in Espírito Santo is new. The reasons for this expansion are still largely unknown,” he said. “The risk we now face is that urban mosquitoes such as the Aedes aegypti could become carriers and then the disease will be transmitted into the cities.”

In a letter to the health ministry, doctors, researchers and academics described the possibility of an urban epidemic as “frightening” and warned that it may already be under way. They urged the authorities to expand the vaccination campaign, improve sanitation and enhance monitoring systems.

But views are mixed. The health ministry insists there is no need for people in the cities to rush to clinics and hospitals for a shot.

Such reassurances have failed to placate the public. Throughout the country, people are queueing up at vaccination centres even in regions that are unaffected.

“What we have is an epidemic of disinformation about yellow fever … People are panicking. There is no reason for this,” said José Alexandre Romano, director of the National Federation of Doctors. He said the ministry needed to provide clear guidelines and updates.

The outbreak highlights the scant resources of epidemiological control authorities in Brazil.

“The government is losing the battle against mosquitoes. The levels of basic sanitation are extremely low, and with this, the tendency is not just an outbreak of yellow fever, but other diseases too,” Romano warned.

This response is in a sharp contrast to that last year for Zika, which was then a new and relatively unknown health threat that was spreading rapidly, associated with birth deformities and for which there was no vaccination.

After Zika was declared a health emergency, the government mobilised more than 100,000 troops and medical personnel to destroy mosquito breeding centres. Worldwide, hundreds of millions of dollars were committed to the search for a vaccine.

However, the worst fears have not been realised, and despite predictions of a second wave of Zika this year, the health ministry said the disease is ebbing.

Last year it killed six people, compared with 629 deaths attributed to dengue and 159 for chikungunya. In November, the World Health Organisation dropped the emergency alert for Zika.