SAO PAULO, BRAZIL - JUNE 21: A boy wearing a Brazilian football shirt walks through the narrow streets of the poor neighbourhood of Itaquera, adjacent to the 'Arena de Sao Paulo' stadium, on June 21, 2014 in Sao Paulo, Brazil. The Arena de Sao Paulo, which is reported to have cost in excess of 200 million GBP, hosted the opening match of the 2014 FIFA World Cup and has a capacity of over 61,000. The total cost borne by Brazil for staging the 2014 World Cup is estimated to be 6.5 billion GBP, which critics have argued would have better spent on the millions of Brazilians living in poverty. (Photo by Oli Scarff/Getty Images)
A boy wearing a Brazilian football shirt walked through the narrow streets of the poor neighborhood of Itaquera, adjacent to the 'Arena de Sao Paulo' stadium, on June 21 in Sao Paulo, Brazil.
Photo by Oli Scarff/Getty Images

Health experts have found polio virus in sewage samples in Sao Paulo, Brazil—a host city for the World Cup. No human cases have been reported and human transmittance is unlikely, according the World Health Organization (WHO).

The samples were taken at Viracopos International Airport in March and tested positive for wild poliovirus type 1 (WPV1) last week. The virus closely resembles the strain of the virus currently spreading in Equatorial Guinea, according to the WHO.

The WHO says the chance of the virus spreading to humans is low. The Sao Paulo region’s high vaccination rates will likely prevent transmission- over 95% of the surrounding population participates in the immunization program.

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Authorities believe the virus to be isolated as the virus has not been reported in surrounding areas and subsequent samples from the same site have tested negative for the virus. However, Brazilian health officials remain on high alert and will monitor the virus closely.

The virus was imported from another infected region, such as Equatorial Guinea, the WHO notes. The risk of exportation of the virus from Equatorial Guinea remains high as the region has low vaccination rates and has been slow to respond to the outbreak. As of June 12, four cases of polio have been reported there.

Polio is a highly contagious virus that affects the nervous system. Most people infected with the virus do not show symptoms, which can facilitate its spreading. For those who do show symptoms, however, the virus can cause life-long or even fatal paralysis. The virus is most commonly spread through traces of fecal matter, sneezing, and coughing. The last reported case of polio in The Americas was in 1991, and Brazil has been WPV-free since 1998, the WHO says.