Officials with WHO believe high immunity to polio among the local population prevented transmission of the disease.
"The vaccination coverage against polio in São Paulo State and Campinas municipality have been higher than 95 percent in the routine immunization program," officials wrote in a press release.
The strain found in Sao Paulo is similar to that of an outbreak in Equatorial Guinea. But while WHO officials say the risk of polio spreading out of Equatorial Guinea remains high, there is minimal risk of contracting the disease in Brazil.
Polio is a virus that attacks the nervous system and can result in paralysis or death if untreated. Many carriers of the disease don't show symptoms, which can enable its spread.
Brazil has been polio free since 1989 and widespread immunization has since become routine.