An infected employee of a vaccine manufacturer was “very likely” the source of the poliovirus particles that were found in a sample from the sewers of the Utrecht Science Park in De Bilt at the end of July. This is the conclusion of the Health and Youth Care Inspectorate (IGJ) on Wednesday after an investigation.
The virus was found in a sample taken from the sewer on July 21. The virus was no longer found during measurements in August and September.
The IGJ examined the faeces of 65 employees of biopharmaceutical BBio and RIVM, which is located on the same site. In the past, they worked with or had access to poliovirus material. That did not yield any results. Blood tests among 101 people showed that a BBio employee has been infected with the virus.
According to the IGJ, the employee in question was well vaccinated and did not become ill after the infection. Mutations in the DNA of the virus sample indicate that the virus did not escape through leakage or discharge in the lab, but ended up in the sewer via the employee, according to the inspection.
Follow-up research at the vaccine manufacturer must reveal how the employee became infected. The IGJ states that there has been no danger to public health, partly because the sewer system in the Netherlands is a closed system and the water purification system switches off poliovirus particles.
The last Dutch outbreak was in the early 1990s
Polio is an incurable disease that can cause permanent paralysis, especially in children under the age of five. Thanks to a strict vaccination policy, the disease no longer occurs in the Western world. Last August, it was announced that wild polio has also been eradicated in Africa.
The Netherlands experienced the last outbreak in 1992 and 1993, among unvaccinated residents of the Biblebelt.
The polio vaccine, which is taken orally, uses a weakened form of the virus.
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