Is Polio Back?

After nearly three decades of absence, polio is making a reappearance in the United States, with its first case being right here in New York. In late July, a young unvaccinated adult living in Rockland County, New York, became the first case of paralytic polio, a type of polio that can cause paralysis in the spinal cord and brainstem, in the U.S. since 2013. After further investigation, this strand of polio has been found in surrounding communities, with new reports revealing that polio has been found in New York City wastewater as well. This spread, combined with lower overall vaccination rates, poses a serious nationwide health risk.

Polio, or poliomyelitis, is a contagious viral illness that attacks the body’s central nervous system. The RNA virus spreads through person-to-person contact, most commonly through contact with the stool of an infected person. Most people who contract the virus (about 72 out of 100) will not have visible symptoms, and will develop flu-like symptoms instead. In most cases, these symptoms fade away on their own within two to five days. However, in extreme cases, the infection can spread to the brain and spinal cord, resulting in diseases like paralysis—the loss or impairment of muscle function in a part of the body.

Dr. Jonas E. Salk licensed the first polio vaccine in 1955. Salk’s vaccine, called the inactivated polio vaccine (IPV), is the only polio vaccine that has been administered in the U.S. since 2000. IPV consists of inactivated poliovirus strains of all three polio variants. When entered into the body through intramuscular injection, IPV stimulates the creation of antibodies in the blood for all three variants and prevents paralysis by blocking the virus from spreading to the central nervous system. By the 1990s, two additional polio vaccines were developed to further contain the virus, and polio was thought to be eradicated from the Americas in 1994. That is, until now.

The patient reported to have poliovirus was identified through the presence of vaccine-derived poliovirus type two (VDPV2) in his stool. Vaccine-derived poliovirus refers to when a strain of weakened live poliovirus contained in oral polio vaccine (OPV), a type of polio vaccine that uses a weakened live form of poliovirus, circulates in the body for long enough to revert to its original disease-inducing form. But because the patient was unvaccinated and had not traveled during the potential exposure period, researchers concluded that the virus had originated from someone who received type two-containing OPV abroad and has since been cycling throughout the US.

Health authorities responded by analyzing the wastewater in Rockland and surrounding counties. From 260 collected wastewater samples from treatment plants in Rockland and Orange County, 21 samples tested positive for poliovirus between the two counties. Specifically, one of the positive samples from Orange County was collected in April, suggesting that this strand has been present in the water since April or earlier.

The investigators followed up by assessing vaccination rates in the patient’s community. According to the New York State Immunization Information System, three-dose polio vaccination coverage among infants and children younger than 24 months living in Rockland County declined from 67 percent in July 2020 to 60.3 percent in August 2022. This decline is largely due to the decrease in routine vaccinations during the COVID-19 pandemic, leaving many communities susceptible to resurgences of vaccine-preventable diseases.

As for next steps, what’s most important now is for everyone to make sure that they are fully vaccinated against the poliovirus. Health authorities have already begun strengthening immunization efforts by supplying IPV to existing clinics and launching new vaccination clinics throughout Rockland County. Now, public health concerns rise as outbreaks are now being seen in other parts of the world. In Israel, seven children have been identified as VDPV positive, and Britain faces a similar predicament as the US with the virus being detected in London’s sewage system. Britain has already responded by offering the polio vaccine to all children aged one through nine. It’s crucial that this vaccination effort also spans beyond the affected countries and becomes a worldwide effort to get rid of polio for good.