A resident of Rockland County has contracted polio, marking the first infection with the virus in the US since 2013, the New York State Health Department has announced. It is thought that the unnamed individual – who is not vaccinated – came into contact with the pathogen after it was brought into the country by someone who had received an outdated form of the vaccine that contains a live yet weakened form of the virus.
Since 2000, the US has administered an injectable vaccine containing an inactive version of the polio virus. Prior to this, the oral polio vaccine (OPV), which includes the live pathogen in harmless amounts, was predominantly offered to all children in the country.
Occasionally, this live virus can replicate and mutate in the gut of an OPV recipient, before being excreted in their stool. Though this won’t harm the vaccinated individual, it can lead to infections in unvaccinated people who come into contact with water that has been contaminated with said poop.
Genetic sequencing confirmed that the infected individual had contracted “revertant polio Sabin type 2 virus” rather than the naturally occurring, wild virus. “This suggests that the virus may have originated in a location outside of the U.S. where OPV is administered, since revertant strains cannot emerge from inactivated vaccines,” explained the New York Department of Health in a statement.
Mainly affecting young children, polio is a highly contagious virus that can cause muscle weakness and paralysis. Once fairly widespread, the illness was eradicated from the US in 1979 following the implementation of a national vaccination program in the mid-1950s.
While the wild virus has not resurfaced in the country, occasional cases of vaccine-derived infections have been reported as a result of travelers introducing the revertant strain from abroad. The last such case involved a seven-month-old baby who had moved to Texas from India in 2013.
Last month, UK health officials announced that a form of the virus derived from OPV was found in London sewage samples.
Globally, cases have decreased by 99 percent since 1988, and all continents apart from Asia are now polio-free. However, the wild virus remains endemic in a small number of countries, with Afghanistan and Pakistan the most notable.
In the US, all children are given a course of three or four doses of the polio vaccine, beginning two months after birth. Fully vaccinated individuals are not at risk of contracting the virus, which is why health officials are now urging everyone in Rockland County to make sure they are covered.
Local vaccination clinics have therefore been set up in the area so that all unvaccinated or at-risk individuals can get jabbed.