Brazilian officials are concerned that a recent yellow fever outbreak will spread to urban areas, threatening the lives of pregnant women, children and other vulnerable groups.
According to the Pan American Health Organization, the number of yellow fever cases spiked at the start of this year, with 206 suspected cases, including 53 deaths, reported in the state of Minas Gerais between Jan. 1 and 18. The organization says four suspected cases of the disease have also been reported in the neighboring state of Espírito Santo, which is considered outside the risk zone for yellow fever.
That is up from just six cases last year, and the highest number since 2003.
The governor of Minas Gerais – the country’s second most populous state – declared a 180-day state of emergency in response to the outbreak. According to Reuters, health officials said they distributed 5.5 million yellow fever vaccines with another 11.5 million to follow in coming days.
Yellow fever is an acute hemorrhagic disease transmitted by infected mosquitoes, much like Zika virus. Symptoms include fever, headache, jaundice, nausea, vomiting, muscle pain and fatigue. Pregnant women, children, the elderly and other vulnerable populations are more likely to develop severe symptoms, which can be fatal within just seven to 10 days. There is no treatment for yellow fever and the supportive care is based on the symptoms.
Jimmy Whitworth, professor of international public health at the London School of Hygiene and Tropical Medicine, told BBC that the current outbreak is “unusual” for Brazil.
“The more cases you have, the more chance that it’s going to light up and take off in urban areas,” he said.
The World Health Organization (WHO) also warned that if the disease continues to spread beyond the state’s borders, it could cause a larger epidemic. States that border Minas Gerais could experience large outbreaks, the organization noted, because the population is not immunized, as these areas were previously thought to be low-risk.
There have been no urban yellow fever cases in Brazilian cities since 1942.
The outbreak comes as Brazil continues to battle Zika, which has led to a spike in birth defects such as microcephaly, a condition marked by an abnormally small head and sometimes debilitating developmental issues.
It is not yet clear what caused the current yellow fever outbreak, but Brazil has never fully eradicated the disease. Brazil’s last recorded yellow fever outbreak, which infected 48 and killed 13, was in February 2008. Before that, the disease afflicted 63 people and killed 23 in 2002-03 in Minas Gerais.
While yellow fever is found in 47 countries across Africa and Central and South America, the overwhelming majority of cases occur in Africa. Last year, Western Africa experienced its worst yellow fever outbreak in several decades, in part due to challenges accessing and distributing vaccines. Vaccines developed nearly a century ago helped eradicate it from most countries. Today, there are as many as 170,000 cases of yellow fever each year. Of those cases, anywhere between 30,000 and 60,000 are fatal.