Doctors informed a patient in the U.K. that he has been shedding a mutated, highly virulent form of the polio virus since receiving immunizations as a child 28 years ago.
According to the Guardian, the patient has been immune compromised since birth. He received standard polio vaccinations at 5, 7 and 12 months of age, followed by a booster injection at the age of 7 years. All of these immunizations took place before he was diagnosed as immunocompromised.
A report about this patient’s case published this week in the journal PLOS Pathogens said that because the man’s body could not properly fight off the weakened polio viruses in his gut, the disease remained in his system, mutated into a more virulent strain and flourished. The man then became a potential disease vector for polio without ever becoming sick himself.
Doctors analyzed stool specimens from the unnamed patient and found live, highly virulent polio viruses. People who have been fully vaccinated are not at risk around such a patient, but people who have not received a full course of immunizations could easily contract the disease.
This poses a huge risk for areas like the developing world, where vaccination programs are still spotty and incomplete. A case like the UK patient could easily spark an epidemic in places where the population is not uniformly inoculated against the crippling disease.
Polio or poliomyelitis is an incurable and potentially fatal viral infection that attacks the brain and spinal cord, resulting in partial or total paralysis and death.
The disease initially appears as a set of flu-like symptoms including headaches, fever, sore throat, tiredness, nausea and stomach pain. These symptoms can last from 2 to 5 days.
A small percentage of patients will go on to experience dangerous inflammation of the covering of the brain and spinal cord (meningitis), paresthesia (a feeling of pins and needles in the legs) and paralysis and weakness in the arms or legs.
These symptoms can be permanent and debilitating, so the threat of patients shedding mutated, contagious versions of the polio virus is very real and — for some — very dangerous.
“These viruses could potentially cause poliomyelitis in susceptible people, so it is very important to maintain high levels of vaccine coverage,” said Javier Martin of the UK National Institute for Biological Standards and Control to the Guardian.
Scientists are close to eliminating polio altogether in most of the world. However, there are three countries where the disease is being actively spread: Nigeria, Afghanistan and Pakistan.
Mutant strains of polio have been found in Britain, Slovakia, Finland and Estonia. To completely eliminate polio from the human population, scientists must track down and eliminate all extant mutations. To that end, the World Health Organization is preparing for a new vaccine trial in spring of 2016.
“We are working on an end-game strategy,” Martin said.