Chicago Department of Public Health Tests for Polio in Wastewater

In an announcement on March 17, 2023, the Chicago Department of Public Health (CDPH) stated that it is testing the wastewater for poliovirus, expanding current analysis and surveillance. The organization said it would begin wastewater testing in Chicago and the Cook County suburbs.

The CDPH is collaborating with scientists at the University of Illinois Chicago, the Illinois Department of Public Health, and several other healthcare organizations. With their help, the organization will test for poliovirus and judge whether any strains are of concern.

Last year, there was growing concern among healthcare providers and public health professionals when a case of paralytic polio was identified in New York state. That case marked the first case in the United States since 2013. The Rockland County Health Department in New York noted that the infected patient had not been vaccinated.

According to the CDC, three different strains of poliovirus cause poliomyelitis. However, type 1 poliovirus is the most common contributor to poliomyelitis since types 2 and 3 were eradicated in 1999 and 2012, respectively.

The disease is often contracted through the mouth from contaminated hands. It can also be transmitted through respiratory particles or oral-to-oral transmission. Although many people, up to 72%, can be asymptomatic while infected, a subset may experience symptoms such as sore throat, tiredness, nausea, headache, and stomach pain. An even smaller portion of the infected population experiences paresthesia, meningitis, and paralysis.

Despite the potential severity of the illness, there are highly effective ways to prevent infection or minimize the risk. The are two kinds of poliovirus vaccines: (1) an inactivated poliovirus vaccine (IPV) and the oral poliovirus vaccine (OPV).

In the US, most clinicians do not recommend using OPV, opting for IPV vaccination to avoid infections that may arise with OPV. CDC guidelines recommend a four-dose series of the IPV vaccine, given at 2 months, 4 months, between 6 and 18 months, and between 4 and 6 years old. Most individuals who get the IPV vaccine in childhood do not need a booster in adulthood; however, high-risk adults may repeat the series later in life.

Recent news has justified the US favoritism for IPV, revealing cases of circulating vaccine-derived poliovirus type 2. According to the Global Polio Eradication Initiative, the cases were identified in Burundi and the Democratic Republic of Congo, linked to vaccination with the novel OPV type 2 vaccine.

Although these cases are far from Chicago, the CDPH is hypervigilant, considering the recent domestic case in New York.

“Polio has been eradicated in the US since 1979; however, a recent case in 2022 in New York State highlights the importance of rapid detection to interrupt any new outbreaks and strengthen routine immunization, which is the best national defense against polio,” said CDPH Deputy Commissioner Massimo Pacilli, in the press release.