An ambitious vaccination campaign is underway in Brazil to counter a large-scale outbreak of yellow fever. Health officials want to inoculate more than 20 million people. International travelers heading to Sao Paulo state are being warned to get their shots before they go.

CGTN’s Paulo Cabral has more.

The first signs that yellow fever had reached the outskirts of Brazil’s biggest city appeared in Sao Paulo’s Horto Florestal Park back in October.  A wild monkey was found dead, killed by the disease. More than 60 others died in the following weeks. It’s a jungle variety of yellow fever, common in the Brazilian countryside. But urban areas are under threat in several states of Brazil, as forests lose ground to development. Several parks were shut for months as a precaution.

The park has now been reopened to the public. But a prominent signs gives visitors a strong warning: “This is a yellow fever risk area. Take a vaccine at least 10 days before coming here.”

Since the beginning of last year there have been 81 confirmed cases of yellow fever in the state of Sao Paulo alone. Thirty-six of those people ultimately died from the disease.  Three other deaths in the state have been attributed to adverse reactions from the yellow fever vaccine.

 People are scared, so getting vaccinated has been a logistical nightmare with supplies unable to keep up with demand. Long lines have been common at clinics around Sao Paulo.

Local business owner Arthur Teja told us, “We went to several clinics around Sao Paulo and we couldn’t find the vaccine anywhere. Then we finally found one where they still have it.”

“I heard a neighbor of mine died of yellow fever and I got really scared,” Sao Paulo resident Rosana Sata told us. “Until now I didn’t believe there was really an epidemic.”

The states of Sao Paulo, Rio de Janeiro and Bahia are beginning a new campaign this week to vaccinate millions more people. They’re using a lower dose of the vaccine to reach a larger percentage of the population. In Minas Gerais, the governor has declared a public health emergency over yellow fever, in order to access federal funds to fight spread of the disease.

State officials say this outbreak is unlikely to become a widespread urban epidemic, because they told us the virus can’t be spread by the type of mosquitos that live in cities.

“It’s a different strain of mosquito,” said Dr. Marcos Boulos, the Sao Paulo State Coordinator for Disease Control. “I believe that this kind of mosquito doesn’t transmit yellow fever.”

But other experts say that’s not at all certain and warn the risk is real.

“There is an actual risk of the disease moving into the cities. It’s still not clear whether the mosquito Aedes Aegypti that we have in urban areas can carry the virus or not,” said Dr. Helio Bacha, who is a coordinator at the Brazilian Society of Infectious Diseases.

All of the cases of yellow fever reported in Sao Paulo have been contracted in the state’s countryside – close to forested areas. It’s a serious situation but one that’s somewhat contained for now.