Brazil is fighting an outbreak of yellow fever that has killed at least 40 people in two months, officials say.
The health ministry said in a report Tuesday that it was the highest rate of deaths recorded from the disease in 14 years.
Yellow fever is carried by monkeys and can be transmitted to humans by mosquito bites.
It can be prevented by a common vaccine.
But the ministry's infectious diseases chief Eduardo Hage told AFP that 22 infections had recently been detected in Espirito Santo state, where vaccines are not carried out because it is considered a low-risk area.
Hage said it was not likely to reach urban non-vaccine areas since there were not enough mosquitos to spread it.
"We are in a state of alert, but there is no cause for panic," Hage said.
The fever cause shivers, aches and vomiting. In severe cases it can be deadly, causing kidney and liver failure and hemorrhages.
Brazil is recovering from an outbreak of the Zika virus, which authorities say has caused brain damage in thousands of newborn babies over the past year.
By AFP's Eugenia Logiuratto in Brasilia.