Brazil: Yellow fever
Brazil: Disease Outbreak News, 24 February 2017
WHO* risk assessment
The growing number of reported cases, the detection of yellow fever circulation in new states, and the
occurrence of epizootics in areas that were previously not considered at risk of yellow fever transmission
indicate that the geographic extent of the outbreak is increasing. Although Brazilian health authorities
have swiftly implemented a series of public health measures to control the outbreak, including mass
[5] vaccination campaigns, it may take some time to reach optimal coverage in some of the areas at risk as
a large portion of the affected populations are dispersed and live in remote locations. It is, therefore,
expected that in the near term additional cases will continue to be detected.
To date, in the three states with laboratory-confirmed yellow fever human cases, there has been no
evidence of transmission by Aedes aegypti; nevertheless, entomological indices in urban centers of these
[10] three states are sufficiently high for sustaining arbovirus transmission, as evidenced by documented
outbreaks of dengue, chikungunya and Zika outbreak in late 2016.
The reports of suspected epizootics in the rural areas of states bordering Argentina, Paraguay, and Bolivia
are a cause of concern as the outbreak may potentially spread to one or more of these countries due
to favourable conditions for yellow fever transmission and suboptimal levels of vaccination coverage.
[15] The introduction of the virus in these countries could potentially trigger large epidemics of yellow fever.
The risk of international spread cannot be formally ruled out but this risk is currently considered to be very
low and limited to unvaccinated travellers returning from affected areas. Viraemic returning travellers
may pose a risk for the establishment of local cycles of yellow fever transmission predominantly in areas
where the competent vector is present.
[20] WHO advice
Advice to travellers planning to visit areas at risk for yellow fever transmission in Brazil includes
vaccination against yellow fever at least 10 days prior to the travel; observation of measures to avoid
mosquito bites, awareness of symptoms and signs of yellow fever, promotion of health care seeking
behavior while traveling and upon return from an area at risk for yellow fever transmission.
[25] As per Annex 7 of the IHR ** a single dose of yellow fever vaccine is sufficient to confer sustained immunity
and life-long protection against yellow fever disease. If, on medical ground, a traveller cannot be vaccinated
against yellow fever, this must be certified by the relevant authorities as per Annex 6 and Annex 7 of the IHR.
The WHO Secretariat does not recommend restriction of travel and trade with Brazil on the basis of the
information currently available.
Adapted from who.int, 24/02/2017
*WHO - World Health Organization
**IHR - International Health Report
The risk of international spread cannot be formally ruled out but this risk is currently considered to be very low (4th paragraph)
According to the text, the risk of an international outbreak can be considered
