A new study based on wastewater samples has shown that there is considerably more mpox DNA than expected based on area cases and hospitalisations, suggesting the virus has been underestimated.

Wastewater epidemiology (WBE) has been increasingly in the spotlight since the COVID-19 pandemic began, as waste samples have been able to predict when new waves will likely occur, and by what strain.

Wastewater is also able to pick up viral DNA from otherwise asymptomatic people who may not be tested for the disease.

Wastewater detection is also helpful when "traditional approaches can miss cases of infected individuals who intentionally do not want to be tested due to the social stigma associated with some diseases, including mpox", said researchers from the Institute of Bioorganic Chemistry Polish Academy of Sciences in Poznan, Poland.

Beginning in May 2022, a global outbreak of mpox began in the UK among men who have sex with men (MSM) and has since infected almost 83,000 people, including 66 deaths, according to the World Health Organisation.

By December 19, 2022, Poznan had 214 reported mpox cases, a relatively small outbreak in Europe. The researchers used samples from two wastewater treatment plants (WTPs) in Poznan to see if DNA samples correlated to the recorded case numbers and hospitalisations.

The detection of mpox virus from mid-September to mid-October did not correlate with the number of reported mpox cases as expected and suggested more viral activity.

This means it's likely that a relatively high number of unidentified mpox-infected people were living among the Poznan population.

"Therefore, in our opinion, all positive samples are related to the non-hospitalised MPV-infected individuals in the general population," the team wrote, in the paper appearing in the International Journal of Infectious Diseases.

The researchers said the findings suggest more people in Poznan were likely infected with such mild cases of the virus that they didn't seek a diagnosis. Additionally, some men likely avoided testing because of the stigma against MSM.

"WBE is a promising additional tool that can complete data gathered by the clinical monitoring approach and predict more accurately the development and progress of the current mpox outbreak," the researchers said.