A strain of poliovirus was found in sewage samples near an airport in São Paulo, Brazil, one of the four host cities of the 2014 World Cup. The government reports no human cases, however.
The samples were collected in March, and no samples collected before or after had the same strains. There is also no evidence that the virus spread through the sewage. Reports say it is completely isolated.
Authorities found the virus during routine environmental inspections in the sewage from the Viracopos International Airport. This is the first positive detection seen in Brazil by environmental surveillance since 1994.
Not to worry, says the World Health Organization (WHO). "[The] virus has been detected in the sewage only...to date no case of paralytic polio has been reported," the organization says in a statement. The specimen found is simply an importation rather than a re-infection. Using genetic sequencing, the strain was matched to a strain from Equatorial Guinea.
With high-traffic travel due to the World Cup occurring in various areas throughout Brazil, the positive samples, while rare, are not entirely surprising or concerning. Brazil has been free of this strain of polio, wild poliovirus type 1 (WPV1), since 1989 and no transmissions have been reported since 1989 either. In the state of São Paulo and its surrounding areas alone, the polio vaccination coverage is above 95%. The next vaccine campaign is scheduled for November 2014, targeting young children between six months and five years old.
As a result, WHO says the risk of international transmission of this virus from Brazil is low.
Equatorial Guinea, on the other hand, has very low immunization coverage. The population exhibits variable degrees of response to the attempts to increase public awareness about polio and the vaccination programs. The risk of international transmission from Equatorial Guinea is, according to WHO, quite high. The Centers for Disease Control and Prevention lately reported four new cases of polio in the small country in central Africa.
Poliovirus is transmitted through contact with an infected person or an infected person's feces. The virus can be spread through water and raw foods. While most people exhibit a few symptoms and then recover entirely, sometimes, though rarely, the virus can lead to loss of muscle function or death.
Environmental surveillance will be heightened, says the Brazilian government. Any transmissions of the virus and any cases of paralytic polio will be found.
