Authorities are puzzled by the origin of a polio virus detected in the Tampere sewage system. They are particularly baffled by the fact that the unknown carrier seems to have all three types of the polio virus.
The virus was first detected in the Tampere sewage system back in December 2008 and has been showing up in the waste system ever since. Since then they have been unable to identify the source of the virus.
This year the virus showed up again in the Tampere waste system, where more than 70 polio virus populations were identified, all of them apparently originating from a vaccine.
The individuals from whom the virus spread into the sewage system are probably unaware that they may be hosting the virus without displaying any symptoms of infection.
Merja Roivainen, lead specialist of the National Institute of Health and Welfare THL said that the virus has been spread by one individual who has received the live vaccine.
The vaccine itself was probably administered 15 years ago, but officials have not been able to pin down a more precise time frame. In other words, it’s not clear if it was administered during a vaccination campaign conducted in Finland in 1985.
Authorities presume that the virus entered the waste system from one person or family.
All three virus types present
The Tampere case has aroused international interest, since all three forms of the virus have been identified.
“Now and then there are cases in which people chronically spread the virus that they have received in a vaccine. However so far no one else has spread all three virus types,” Roivainen noted.