Brazil has confirmed 723 cases of yellow fever, putting the current outbreak on track to surpass the previous, unusually large one.

The Health Ministry said Thursday that 237 people have died from the disease. During the same period in the 2016-2017 outbreak, Brazil recorded 576 infections and 184 deaths. For nearly a decade before that, Brazil never recorded more than a handful of cases each year.

The ministry says the disease is now circulating in more-populated areas, resulting in more infections. The populous states of Sao Paulo and Minas Gerais have been most affected in this outbreak.

Both the previous and current outbreaks have affected areas not previously considered at risk for the disease and where vaccination was not routine. Brazil is now trying to vaccinate millions against the virus.