Poliovirus detected in Tampere wastewater, but no cases reported

By admin On Dec 9, 2024

The Finnish Institute for Health and Welfare (THL) has identified a mutated type 2 poliovirus (VDPV2) in wastewater samples collected in the Tampere region in November. This strain, derived from an oral polio vaccine, is similar to findings reported in several European countries this autumn. Despite the detection, no cases of the disease have been identified, and Finland maintains high vaccination coverage against polio.

The presence of VDPV2 in wastewater indicates that one or more individuals in the area were shedding the virus at the time of sampling. If an unvaccinated or partially vaccinated person encounters this virus, there is a risk of infection and, in rare cases, symptomatic polio.

Leif Lakoma, Chief Physician at THL, described the detection as rare but not unexpected. “A similar finding was made in Finland about ten years ago. The risk of a polio epidemic in Finland remains low. We have one of Europe’s best surveillance systems for polio, and our vaccination coverage is high,” he said.

Poliovirus monitoring through wastewater is conducted in several European countries. Similar detections of mutated type 2 polioviruses have been reported this year in Spain, Poland, and Germany. Genetic analysis by the World Health Organization (WHO) linked these viruses to a strain initially identified in Nigeria, which continues to circulate in several African countries. No cases of polio have been reported in Europe.

Polio vaccination in Finland began in 1957, and the last case was recorded in 1985, the same year a booster vaccine was offered to the entire population. Currently, Finland uses an injectable polio vaccine that does not contain live viruses, eliminating the risk of vaccine-derived infections. This vaccine is provided free of charge under the national vaccination programme.

Polio vaccination coverage among children in Finland exceeds 98%. The vaccine is administered at three, five, and 12 months of age, with a booster at four years old. Adults are advised to ensure they have received three doses of the polio vaccine over their lifetime.

Hanna Nohynek, Chief Physician at THL, urged individuals to check their vaccination status. “It’s important to ensure that everyone in your close circle is fully vaccinated. This is particularly relevant for adults who have come to Finland from abroad for work or study, as their childhood vaccination records may be incomplete,” she said.

Travellers to regions with a higher risk of polio infection are recommended to receive a booster dose if their stay exceeds four weeks and their last booster was over a year ago.

Since 2014, WHO has classified polio as a global public health emergency. In Finland, polio remains a nationally notifiable disease. The virus spreads through the digestive tract, often via contact with contaminated surfaces, food, or, more rarely, respiratory droplets. In some cases, the virus can spread to the central nervous system, causing paralysis and muscle atrophy.

Europe eliminated wild poliovirus over 20 years ago, but vaccine-derived poliovirus strains are occasionally detected in wastewater. These strains pose little risk of further transmission. However, isolated cases of polio caused by mutated vaccine-derived strains have occurred, such as in Ukraine in 2021 and Israel in 2023.

While Finland uses the injectable polio vaccine, many countries still rely on the oral vaccine, which contains live virus and provides stronger mucosal immunity. WHO is developing a new plan to phase out the live oral polio vaccine to reduce the risk of vaccine-derived strains, highlighting the urgency of eradicating all forms of poliovirus.

Source: www.helsinkitimes.fi