Polio virus has been found in sewage water sampled at an international airport in the state of São Paulo, Brazil, hosts of the 2014 World Cup. However, the authorities, who confirmed the finding on June 18th, believe the isolated virus sample is most likely imported as it matches a strain currently circulating in Equatorial Guinea.

The World Health Organization (WHO) say based on current evidence, Brazil – which has been free of polio since 1989 – is not considered to be affected by the disease.

Polio (full name poliomyelitis) is a highly infectious disease caused by the wild poliovirus (WPV) and can cause paralysis or even death in a matter of hours. The virus enters the mouth in water or food contaminated by fecal material from an infected person.

The Brazilian sample found to contain wild poliovirus type 1 (WPV1) was collected by routine surveillance in March 2014 at Viracopos International Airport, in the Campinas municipality of the state of São Paulo. The virus was detected in sewage only – subsequent samples have tested negative for WPV1, and there have been no reports to date of cases of paralytic polio, say the WHO.

The sample was detected as part of routine surveillance set up under the auspices of the International Health Regulations (2005), where member states are required to designate a National IHR Focal Point that can be accessed at any time by the WHO.

Samples have been collected at Viracopos airport and other sites throughout Brazil since 1994 and apart from this isolated event, have consistently tested negative for WPV, say the WHO.

The Brazilian health authorities have stepped up surveillance aimed at detecting spread of WPV1 and potential cases of polio, and also to identify any people not vaccinated for the disease.

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Polio was detected in Brazil as part of routine surveillance set up under the auspices of the International Health Regulations.

The WHO consider the isolated event – in the absence of further evidence – to be a case of importation rather than indigenous transmission. Genetic sequencing has shown that the isolated strain of WPV1 closely matches a strain recently found in Equatorial Guinea.

The West African country is experiencing an ongoing outbreak of polio, and the WHO consider the risk of further exportation of polio virus to be high.

Vaccination against polio has been high in Brazil. The last national oral polio vaccine (OPV) campaign was conducted in June 2013, and routine immunization rates in São Paulo state and Campinas municipality have been higher than 95%. The 2014 OPV campaign in Brazil will take place in November and will target children aged from 6 months to under 5 years.

Meanwhile, the WHO’s International Travel and Health recommends “all travellers to and from polio-affected areas be fully vaccinated against polio,” and notes, “Brazil has detected a poliovirus importation event. Based on current evidence, the country is not considered polio-affected.”

In April 2013, Medical News Today reported how the WHO plan to eradicate polio by 2018. The WHO, Rotary International and the Gates Foundation – major supporters of the Global Polio Eradication Initiative (GPEI) – said that the goal was reachable, given that polio cases had dropped to only 223 per year.