There is a little risk for the public, British health officials emphasize, but those who are not fully vaccinated against polyovirus are urged to get their shots. This is very important for young children.

Most of the British population will be protected from vaccination in the future, but in some communities with low vaccine scope, individuals may remain risky,” Dr. Vanessa Saliba, an epidemiological consultant for the British Health Security Agency, said in an agency agency statement.

The sample genetic analysis refers to the same origin. It is likely that someone who travels to England around the new year, Dr. Shahin Huseynov, a technical officer for the Disease and Immunization Program of the World Health Organization Vaccine in Europe, told The New York Times.

The four newest samples collected can be in small children who are introduced to viruses by this person or each other.

It is also possible that all samples came from one immunocompromised person who had released the virus for months, the agency added.

The big problem here is whether it continues to circulate in England or whether it is a more immunoden person,” Dr. Walter Orentein, Associate Director of the Emory Vaccine Center and former Director of the United States Immunization Program, told The Times.

Wastewater treatment plant from which the sample was taken covering around 4 million people, said Times. The sample collection continues to try to identify the source.

Is typical for waste supervision to take one or two cases of polio every year. The last polio case confirmed in England was in 1984. The country was declared polio free in 2003.

When someone is infected, the virus lives in the intestine and appears in the feces. This most often spreads when infected people touch food or water intended for others without washing hands.

Poliovirus can infect the spine and cause paralysis, which occurs in about 1% of patients.

Most of these diseases do not show symptoms, only about one in 500 children who are truly paralyzed,” Dr. David Heymann, an infectious disease expert in the London School of Hygiene and Tropical Medicine, told The Times. He previously led the Polio Eradication Program in the World Health Organization.

Wild polio now only exists in Afghanistan and Pakistan, but the “live” oral vaccine is used in some parts of the world and can be briefly spilled in the feces of someone immunized.

Health officials think that is what happens here because the virus in the sample matches the type of oral polio vaccine used to contain outbreaks, said Huseynov. The vaccine was used in Afghanistan, Pakistan and several Middle Eastern countries and Africa in recent months.

Polio continues in some of the poorest parts in the world. To be eradicated throughout the world, the risk of import and spread in the UK and elsewhere will continue, “Nicholas Grassly, a vaccine epidemiologist at Imperial College London, told The Times.

Britain uses inactive polyovirus that is injected for vaccination. That cannot be shed through dirt. London has a polio vaccination level of around 86.6%, according to the Global Polio Eradication Initiative.