Following detection of paralytic polio in a young adult in New York, the Centers for Disease Control and Prevention (CDC) is reminding clinicians how to recognize and report polio while reinforcing the importance of routine childhood polio vaccination.
The guidance was outlined in a Sept. 1 webinar, which can be viewed at https://bit.ly/3qf74eF. Speakers also discussed how to distinguish polio from conditions with similar symptoms.
Ruling out polio
It’s important to rule out polio in cases of unexplained acute flaccid paralysis (AFP).
Paralytic polio can resemble acute flaccid myelitis (AFM), acute cord compression, transverse myelitis, spinal stroke and Guillain-Barré syndrome.
To help guide diagnosis, patients should undergo a thorough medical history, neurological examination, lab testing and MRI of the spine and brain. Polio is characterized by lesions in the gray matter of the spinal cord, which are visible on MRI.
A stool specimen is the gold standard for detecting poliovirus. Health care providers should not wait for the results of specimen testing to manage patients or report suspected cases to public health authorities.
Before the onset of acute flaccid weakness in polio, most patients have an illness, such as gastrointestinal illness with fever, sore throat, abdominal pain, muscle aches and malaise. The weakness might occur one to three weeks after the illness or within hours or a few days.
Another symptom to watch for is loss of muscle tone and reflexes.
“We instruct parents and frontline clinicians to think acute flaccid myelitis or polio when faced with a child with limb weakness … In other words, that limb is floppy not spastic,” said Janell Routh, M.D., M.H.S., CDC incident manager for the New York polio response and a captain in the U.S. Public Health Service. “Paralytic polio weakness is usually in the lower extremities and often asymmetric. This is contrasted to acute flaccid myelitis, where although we see that same asymmetry, it is mostly the upper extremities that are affected in that disease.”
Bulbar polio presents with cranial nerve findings, such as difficulty with eye movement, facial droop or difficulty swallowing and slurred speech. Infants may have a weak or hoarse cry. These symptoms can signal respiratory impairment.
Clinicians also should evaluate strength in the proximal as well as distal muscle groups.
Red flags for polio include recent international travel to areas where poliovirus is circulating and within the incubation period, usually seven to 21 days; exposure to someone infected with poliovirus; and being unvaccinated, undervaccinated or having unknown vaccination status.
“When I walk into an examination room with a child who has acute flaccid weakness, the first question out of my mouth should be: Does that patient have the full complement of recommended polio vaccinations?” Dr. Routh said.
New York case spurs outreach
The detection of poliovirus in New York has led to a large response involving education and outreach, deploying vaccine to the affected areas and encouraging immunization, said Emily Lutterloh, M.D., M.P.H., director of the Division of Epidemiology at the New York State Department of Health.
“We know that there are some people who like to delay the vaccine series until right before the child enrolls in school, where it’s required, but unfortunately, that leaves very young children … who are often cared for in groups … unprotected,” she said.
The department is continuing enhanced surveillance, including trying to discern the prevalence of asymptomatic infection in affected areas. One example is working with pediatricians to collect stool samples from diapers if a patient has a soiled diaper while in the office and with parental agreement.
Paralytic polio occurs in less than 1% of infections.
“For this reason, one case of paralytic polio indicates an outbreak,” said Lt. Cdr. Farrell Tobolowsky, D.O., M.S., of the U.S. Public Health Service and CDC clinical task force lead for the 2022 New York polio response. “There are likely many infected, with about 25% that have a mild clinical illness and the majority, or about 75%, (who) have an asymptomatic infection.
“Even those with asymptomatic or mild infection can shed the virus,” she said.
The inactivated polio vaccine (IPV), the only one used in the U.S. since 2000, is highly effective: 90% of recipients are immune after two doses, and 99% are immune after three doses.
Wild poliovirus 1 remains endemic in just two countries, but vaccine-derived poliovirus outbreaks continue, with 249 laboratory-confirmed cases this year.
“The oral polio vaccine (OPV) prevents both paralysis and transmission and has been instrumental in eradicating wild polioviruses around the world because it stops the spread of the virus. It is … the current vaccine of choice for most countries experiencing outbreaks,” Dr. Tobolowsky said.
Because OPV contains weakened live virus and is shed in stool, it can circulate in a community. If it circulates in an underimmunized population for long enough, the strain can revert to a form that causes paralysis.
“It is critical to maintain high vaccination coverage worldwide, including in the United States,” Dr. Tobolowsky said.
- CDC webinar on recognizing and reporting polio
- CDC resources for health care providers on poliomyelitis
- The CDC poster “Head Shoulders Knees & Toes” can help assess strength in muscle groups
- Global Polio Eradication Initiative
- AAP News article “Sudden onset of limb weakness could signal acute flaccid myelitis or polio”