So far no cases of polio have been identified and the risk to the public is low. However, health authorities have urged anyone who is not fully immunized against the polio virus, especially young children, to seek vaccines immediately. “Most of the UK population will be protected from childhood vaccination, but in some communities with low vaccination coverage, people may remain at risk,” she said. Vanessa Saliba, epidemiological consultant for the United Kingdom Health Insurance Agency. The last polio outbreak in Britain was in 1984 and the country was declared polio-free in 2003. Prior to the introduction of the polio vaccine, epidemics were common in Britain, with up to 8,000 cases of paralysis reported each year. Regular sewage monitoring in the country detects the polio virus once or twice a year, but between February and May, officials detected the virus in several samples collected in London, according to Dr. Shahin Huseynov, World Health Organization’s Vaccine Technician in Europe. Genetic analysis suggests the samples are of common origin, most likely a person who traveled to the country on New Year’s Eve, Dr. Huseynov said. The last four samples collected appear to have evolved from this initial introduction, most likely in unvaccinated children. “The significance of this finding is that even in well-developed countries, in countries where standard vaccination coverage is quite high, it is still important to ensure that all children have access to vaccines,” he said. British officials are now collecting additional samples and trying to identify the source of the virus. But the sewage treatment plant that located the samples covers about 4 million people, almost half of the city, which makes it difficult to locate the source. Polio is most often transmitted from an infected person who does not wash their hands properly and then touches food or water that has been swallowed by someone else. The virus thrives in the intestine and emerges in the feces of infected people. In up to 1 percent of patients, the virus can infect the spine and cause paralysis. “Most of the disease is asymptomatic, it is only one in 500 children who are actually paralyzed,” said Dr David Hayman, an infectious disease specialist at the London School of Health and Tropical Medicine who had previously led the eradication program. WHO polio. In Britain, the polio vaccine is given by an injectable inactivated polio virus, which cannot be excreted in the faeces. However, some countries around the world rely on an oral polio vaccine that contains a live, attenuated version of the virus. Immunized individuals can excrete this virus in their feces for a while, which can then appear in the sewage. This is what health officials believe happened in this case. The virus in the samples collected came from a type of oral polio vaccine used to reduce outbreaks, according to Dr. Huseynov. In recent months, this type of vaccine has only been used in Afghanistan, Pakistan and some countries in the Middle East and Africa, he said. The wild polio virus has been eradicated from all over the world except Afghanistan and Pakistan. But vaccine-borne polio continues to cause small outbreaks, especially in communities with low vaccination coverage. “Polio persists in some of the poorest parts of the world. “Until it is eliminated worldwide, the risk of importation and spread to the UK and elsewhere will continue,” said Nicholas Grass, a vaccine epidemiologist at Imperial College London. The analysis so far suggests transmission from the community, most likely among young children. A less likely one is that an individual immunosuppressed person has had the virus eliminated for months. “The big question here is whether it is constantly circulating in the UK or whether it is an immunocompromised person,” said Dr Walter Orenstein, deputy director of the Emory Vaccine Center and former director of the United States Vaccination Program. If it is the latter, Orenstein said, “they must find this immunodeficient person.”
