World Health Organisation (WHO) chief Tedros Ghebreyesus has said a ceasefire in Gaza is “essential to allow an effective response” to the threat posed by the presence of poliovirus in the Palestinian territory, Al Jazeera reports.

Following the discovery of virus samples in wastewater and sewage in Khan Younis and Deir el-Balah areas, the WHO, Gaza’s Ministry of Health, the UN’s children’s agency (UNICEF) and the agency for Palestinian refugees (UNRWA) have started a “risk assessment”, Tedros said in a post on social media.

The assessment aims to identify “the scope of poliovirus spread and the necessary response to stop any further spread, including prompt vaccination campaigns”, he said.

Gaza’s decimated health system, displaced population, and lack of access to clean water and proper sanitation “poses a risk for children and creates the perfect environment for diseases like polio to spread”, Tedros added.