Yellow Fever Outbreak in Brazil Causes Hundreds of Deaths


A yellow fever outbreak that started in December 2016 with only six human cases in just three states has now spread across the country, infecting thousands and killing hundreds.

Updated March 14, 2017 at 9:45 AM EST

On March 2, 2017, the Pan American Health Organization (PAHO) reported thousands of cases of yellow fever and hundreds of deaths across the country.

Last month, the Ministry of Health of Brazil declared that a yellow fever outbreak that had started in December 2016, was ongoing. As such, the Centers for Disease Control and Prevention issued a travel alert, recommending individuals “practice enhanced precautions” when traveling to Brazil. Now, PAHO reports that there has been a total of 1,368 yellow fever cases and 220 associated deaths in humans across the country as of epidemiological week 7 of 2017.

Unlike with the Zika virus, there is currently a yellow fever vaccine, which is 80%-100% effective within the first 10 days of vaccination, and 99% effective after 30 days of initial vaccination. Unfortunately, however, the vaccine is not widely available, and, therefore, it can only be administered to those in areas at highest risk of transmission. In an exclusive interview with Contagion®, Marta Cavalcanti, MD, PhD, physician at Infectious Disease Clinic, Hospital Universitario Clementino Fraga Filho, UFRJ, Brazil, said, “In the areas where [yellow fever] transmission does not occur, vaccines are not available.” Even still, she went on to explain that, “We have a number of vaccines that [we] planned ahead [for] to protect our population during the whole year,” but if there is a rapid increase of cases or new areas identified to have active transmission that were not planned for, there will not be enough vaccines to go around.

In February alone there was a total of 376 new human cases, both confirmed and probable. According to PAHO, the current case count is as follows: 326 confirmed, 125 discarded, and 916 suspected cases under investigation. Of the total deaths, 109 were in confirmed cases, 6 were in discarded cases, and 105 were in cases under investigation. According to the Situation Summary, “the case fatality rate (CFR) is 33% among confirmed cases and 11% among suspected cases.”

PAHO has identified the state of Minas Gerais to be the largest site of infection, with 83% of all confirmed (269 cases) and suspected cases (940 cases). The rest of the affected states are far behind, with Espírito Santo taking the lead with 132 suspected cases and 53 confirmed cases. Espírito Santo is followed by São Paulo with six suspected and four confirmed cases, Bahia with nine suspected cases, Tocantins with two suspected cases, Goías with one suspected case, and Rio Grande do Norte with one suspected case. There are also five suspected cases for which PAHO has yet to determine the initial area of infection. Furthermore, the CFR is reported to be 75% in São Paulo (3 deaths), 34% in Minas Gerais (92 deaths), and 26% in Espírito Santo (14 deaths).

Nevertheless, PAHO reports that there has been a “downward trend” of cases reported out of Minas Gerais, and that the organiziation will continue to monitor yellow fever in all regions of the state.

Yellow fever does not stop there, however. According to the Situation Summary, there has been a total of 386 confirmed yellow fever cases identified in nonhuman primates during this outbreak, with an additional 8 cases having been discarded; this number is up by 76 (which are currently being investigated) since February 24, 2017. These cases were identified in the Federal District, as well as the following states: Alagoas, Bahia, Goiás, Espírito Santo, Mato Grosso do Sul, Minas Gerais, Paraná, Pernambuco, Rio Grande do Norte, Rio Grande do Sul, Santa Catarina, São Paulo, Sergipe, and Tocantins.

While Aedes aegypti is the main yellow fever vector, according to PAHO, “to date, Aedes aegypti has not been reported to have a role in transmission.”

Currently, Colombia, Peru, and the Plurinational State of Bolivia have reported yellow fever activity. Although no cases of yellow fever associated with the ongoing Brazilian outbreak have been reported in these or other neighboring countries, it is a growing threat since epizootic reports are currently under investigation in states that border Bolivia, Paraguay, Argentina, and Uruguay.

Update: Vaccination efforts have commenced in several cities in the states of Minas Gerais as well as Espírito Santo. Now, The Rio Times reports that Rio de Janeiro has requested that the entire state population be vaccinated against yellow fever. Although there have been no cases of yellow fever identified in humans in Rio de Janeiro thus far, a state-wide precautionary vaccination campaign will immunize 1.5 million individuals monthly for one year, until 90% of the state's population is vaccinated. According to state health officials, approximately 12 million vaccine doses will be needed to reach 90% immunization rates.

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