WHO EMRO | Supervision | About eradication

Environmental monitoring officers collect wastewater samples during the environmental monitoring activity in Mogadishu, Somalia.

Quality surveillance is the foundation for the polio eradication initiative. Surveillance both detects the presence of poliovirus and informs the program’s actions—typically, whether to launch a vaccination campaign in response to disease detection, and if so, what kind of campaign. As the world moves closer to polio eradication, surveillance becomes increasingly important: the final determination to certify the Eastern Mediterranean Region free of wild poliovirus will rest on the basis of surveillance data. Consequently, in the region, the world’s last with transmission of wild poliovirus, the program a significant amount of funding and expertise in the establishment, maintenance and improvement of polio surveillance networks.

How polio surveillance works

Polio surveillance is the practice of exhaustively searching for poliovirus in its only known reservoir – humans. This is done in two ways: through surveillance for acute flaccid paralysis (AFP), the primary symptom of poliomyelitis infection, and through surveillance of sewage effluent, to look for virus shed in the stools of infected people. AFP surveillance is known as the gold standard of polio surveillance, but environmental surveillance is playing an increasingly important role in the region. For both practices there is a set of clear surveillance indicators that must be met.

Acute flaccid paralysis (AFP) surveillance

The polio program relies on a large network of health care workers, traditional healers, pharmacists and community leaders across the region to look for and report any case of AFP in their community. The main sign or symptom of poliomyelitis, the disease caused by poliovirus, is acute flaccid paralysis (AFP). It is mainly seen in children under 15 years of age. Consequently, the aim of AFP surveillance is to detect, report and investigate all AFP cases so that poliomyelitis can be ruled out as the cause of the paralysis.

When a person is reported with AFP, a polio surveillance officer travels to their home or the nearest health clinic to collect stool samples. These samples are transported to a WHO-accredited polio laboratory for testing and analysis, to see if poliovirus is present. The journey to the laboratory can be long, and a key challenge for polio surveillance officials is keeping the samples at a constant low temperature while traveling in cars, on foot, on a donkey, motorbike, boat or plane. This is called the reverse cold chain, and maintaining it so that the sample arrives at the laboratory in a testable condition is a critical performance indicator of AFP surveillance.

These are the four steps of AFP surveillance

Find and report children with AFP Transport stool samples for analysis Isolate poliovirus Map the virus

Environmental monitoring

Environmental surveillance involves testing sewage runoff for the presence of poliovirus. Because most cases of poliomyelitis are asymptomatic, but all infected people shed virus in their stools, environmental surveillance has the advantage that we can detect the presence of polio in an area before any case of paralysis occurs.

In places that are polio-free, regular environmental surveillance allows us to detect any new emergence or international spread of polioviruses – a significant threat until polio is eradicated. Environmental surveillance also enables the program to assess the quality of outbreak response, as it can detect the vaccine virus used in immunization activities. Genetic data analysis of polioviruses detected through sewage runoff can also show how viruses are related to each other, helping exterminators map their paths of transmission and determine the extent of the vaccination response, if appropriate.

Between 2020 and 2021, the polio program expanded its environmental surveillance network in the region, particularly in Afghanistan, Egypt, Somalia and Sudan. Work has also begun in Djibouti, Iraq, Saudi Arabia and Yemen to establish laboratory capacity for environmental surveillance.

The Eastern Mediterranean Region Polio Laboratory Network (EPLN)

The Eastern Mediterranean Region Polio Laboratory Network was established in 1991 by the WHO and national governments. Its key role is to provide virological information that can be used to direct resources towards the eradication and, in the case of imports, the spread of wild polioviruses.

The Network consists of 12 laboratories in a three-level structure: national laboratories, environmental surveillance laboratories and intratypic differentiation laboratories.

At 12 national laboratories in Egypt, the Islamic Republic of Iran, Iraq, Jordan, Kuwait, Morocco, Oman, Pakistan, Saudi Arabia, Sudan, Syria and Tunisia, polioviruses isolated from faecal samples collected from AFP cases are tested with standardized procedures and reagents. Countries without national laboratories are served by others in the network: Afghanistan is served by Pakistan; Bahrain, Qatar, United Arab Emirates and Yemen are served by Oman; Lebanon is served by Syria; Libya is served by Tunisia. Djibouti, Somalia and Yemen are served by the Kenya Medical Research Institute (KEMRI) laboratory which is not part of the Eastern Mediterranean Region network.

There are seven environmental monitoring laboratories across the region, in Egypt, Jordan, the Islamic Republic of Iran, Kuwait, Pakistan, Sudan and Syria. These laboratories support the environmental surveillance activities for their own countries, although the Syria laboratory also tests samples from Lebanon. Djibouti, Somalia and Yemen are served by KEMRI.

The EMR also has 10 intratypic differentiation laboratories, in Egypt, the Islamic Republic of Iran, Jordan, Kuwait, Morocco, Oman, Pakistan, Saudi Arabia, Syria and Tunisia, which perform intratypic differentiation of isolates to confirm whether they are wild poliovirus, vaccine is. -derived polioviruses, or vaccine virus.

All networks perform real-time reverse transcription-polymerase chain reactions (rRT-PCR) for intratypic differentiation laboratories and screening of vaccine-derived polioviruses. There are 5 in the region (Pakistan, Tunisia, Egypt, Oman and the Islamic Republic of Iran). All wild viruses are subjected to nucleotide sequencing to monitor the virus transmission pattern and relationships.

The Polio Laboratory Network in the Eastern Mediterranean region is regularly subject to accreditation visits; separately, the network’s senior supervisors meet annually to develop recommendations to improve performance and adopt new technologies and methods.

Related links

Reports of intercountry meetings for directors of polio laboratories in the region

Supervisors in the region

Regional Polio Bulletin

The impact of the COVID-19 pandemic on poliovirus surveillance

Although surveillance systems across the region have been affected by the COVID-19 pandemic, regional surveillance has continued to operate throughout the pandemic and has done so in accordance with special guidelines set by the GPEI to ensure the safety of workers. What’s more, the polio surveillance network, in both the field and the laboratory, supported the pandemic response by setting up surveillance for reporting and tracking of COVID-19 cases, contact tracing, laboratory testing and data management.

Even with this increase in workload and the complexities caused by the COVID-19 pandemic, most countries in the region have met and continue to meet global standards for surveillance indicators.