World Health Organization spokesman Christian Lindmeier confirmed on Tuesday that the emergence of polio cases in the Gaza Strip could represent a setback for international efforts to eradicate the disease, suggesting that cases of the disease may emerge in the Strip.

Lindmeier told a news conference at the United Nations that Gazans may have already been infected with the disease, but it is difficult to detect cases of this deadly virus because most of them are asymptomatic.

He added: "Finding vaccine-derived poliovirus in wastewater indicates that it is present in some people, which represents a high possibility of an outbreak of the virus, and this would represent a major setback to global efforts."

“An investigation and risk assessment is still ongoing in the sector,” Lindmeier added.

Return of polio epidemic

The Ministry of Health in Gaza announced in a statement the return of the polio epidemic to the Strip late Monday evening after samples of the disease virus were found in sewage water. However, it has not yet announced the emergence of any cases of infection with the disease.

The Ministry of Health said in a statement: “We declare the Gaza Strip a polio epidemic area, and this poses a health threat to the residents of the Gaza Strip and neighboring countries and a setback to the global polio eradication program.”

One million doses of polio vaccine

Last Friday, WHO Director-General Tedros Adhanom Ghebreyesus said the organization would send more than a million doses of polio vaccine to Gaza.

He pointed out that the vaccine will be distributed over the coming weeks to prevent children from being infected after the virus was detected in samples of sewage water in the sector.

“Although no cases of polio have been reported so far, without immediate action, it will only be a matter of time before thousands of children become infected and become unprotected,” Ghebreyesus said in an opinion piece in the British newspaper The Guardian.

The Director-General said children under five are most at risk of contracting the virus, especially infants under two years of age, as regular vaccination campaigns have been disrupted by the nine-month-old conflict.

More than nine months of conflict have caused polio vaccination rates to drop from 99 to 89 percent, said James Elder, a spokesman for the United Nations Children's Fund (UNICEF), expressing concerns about vaccines reaching those who need them given the restrictions on humanitarian access to the Strip.

“It is difficult to distribute the vaccine amidst mass displacement, destroyed infrastructure and an extremely unsafe working environment, so many children will be at risk of contracting the disease,” he added.