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Understanding the Polio Surveillance System

Watch Riris Adondo Ahmad explain key features and considerations of the polio surveillance system. (Step 2.6)
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SPEAKER: Polio surveillance rely on Acute Flaccid Paralysis surveillance. We use both, passive, in which health care workers routinely reporting cases, and active surveillance, in which we try to actively find case in community. So why we need AFP instead of polio cases? Yes, because several other conditions may look like polio, such as Guillain-Barré Syndrome, and just relying on what clinician thinks is polio means that some cases of polio will be missed. So information on all quick-onset floppy paralysis in children is collected by the polio surveillance system.
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Here we see Dr. Siddique, a focal point for Acute Flaccid Paralysis, examines a child in Mirwais Regional Hospital in Kandahar, Afghanistan. So now, let’s discuss the AFP surveillance processes. But before that, I would like you to describe the process of the surveillance system from your reading, right. AFP surveillance process consists of One, finding and reporting children under 15 years old with AFP. Here, Surveillance Medical Officer [? pore ?] [? over ?] medical record in the health facility across the world. Second, transporting stool sample for analysis, as in the photo here. Two-two samples from every child with AFP, taken hours apart, are carefully packaged and stored by the Surveillance Medical Officer.
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This photo is from Bangladesh, and shows stool samples ready to be transported to the National Polio and Measles Laboratory in Dhaka. Its samples must travel with [? full ?] ice pack and must reach the lab within 12 hours of having left the hospital, even when traveling from the furthermost district of Bangladesh. The third step is isolating the polio virus in the laboratory. In this picture, we see a sample, [? and ?] this [? is in ?] room. Its delivery is recorded. And in 2014, in Bangladesh, there are 3,112 samples, were received and processed at this laboratory from all over Bangladesh.
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From here they are taken into sample processing room in isolation, the sample is open and process, and this process can take 2 to 5 days. And then we need to do mapping of the virus to determine the origin and the strain of the virus.
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Now we will discuss about the AFP surveillance pathway. A good polio surveillance system should be able to detect and notify AFP cases early. And within 14 days or less, the polio surveillance staff is required to do case investigation, and collect stool specimens for laboratory confirmation. The specimen collected, should arrive at the designated National Laboratory within three days after leaving the health facility that collect the specimens. It takes another 21 days to culture the specimens and to confirm the existence of polio virus in the stool sample. And it takes another few days to do lab test to determine the presence and the type of polio viruses.
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If, for some reason, they could not get adequate stool sample, a follow up examination need to be conducted after 60 days of the onset paralysis. All these processes, and the final classification of the virus need to be finished within 90 days from the onset of the AFP symptom. If, for some reason, they could not get adequate stool sample, a follow up examination need to be conducted after 60 days of the paralysis onset. All of these processes, and the final classification of the virus need to be finished within 90 days from the onset of the symptoms. So, with that in mind, what might be some challenges in achieving all of this in some contexts?
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Maintaining high quality AFP surveillance is critical to achieving a system that is sensitive enough to detect polio virus anywhere in a country. Yet, in practice, challenges detects sufficient sensitivity in AFP surveillance because one, AFP surveillance itself does not operate effectively, or because the program is unable to routinely access [? all ?] its special population with AFP surveillance. Or three, the broader health infrastructure is too weak or non-existent, to support AFP surveillance. And in some countries, particularly polio-free countries, attention to and funding for AFP surveillance is declining.
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And all the data from the countries are sent to WHO regional offices and then uploaded in WHO Polio Information System, or we call POLIS. POLIS was designed to harmonize, consolidate, perform quality checks, and perform analysis of data from AFP surveillance, environmental surveillance, supplemental immunization activities and laboratory testing. The compilation of this data in POLIS result in a central repository that permits access to standardized data, analysis, and outputs that are readily available to countries, and WHO regional offices, as well as to a wider spectrum of users such as GPEI partners. And outputs include country profiles as they relate to polio eradication, table, maps line lists, and other graphics.
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One, is the challenge in polio surveillance, is access to compromised area. This is because the last remaining cases are in those area, for example, in Afghanistan, in Pakistan. In this slide, we can see that Afghanistan can maintain the sensitive surveillance in across all access category. If we can maintain this quality we can ensure that we will not miss the cases in those area, and we can ensure the eradication of polio in the world.
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As you can see here, this is a report of AFP surveillance in Yemen from 2018 and 2019. We can see table of AFP Classification versus Accessibility of District. There are three different district categories according to the accessibility. If we compare what happened in 2018 and 2019, all the AFP finding decrease between these two years. But we can see that it decreased even more strongly in area with inaccessible districts. So it means that we will miss a lot of AFP cases in this area. And if we miss cases of AFP we may also miss a case of polio.
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To understand if surveillance is happening at the quality and level that is hopeful, the GPEI use a number of performance indicators, as we see in the slides. For example, one indicator is number of AFP cases. Another one is percentage of AFP cases investigated within 48 hours. Percentage of AFP cases with two adequate stool specimens collected for 24 to 48 hours apart, and within 14 days after onset. Percentage of specimen arriving at a laboratory in a good condition. Percentage of specimen arriving at a WHO-accredited laboratory within three days of being sent. And a percentage of specimens for which laboratory result are sent within 28 days of their receipt. Why do you think this performance indicator would be so important?
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Correct, because these indicators will tell us what are the quality of its steps of the surveillance pathways. And, for example, percentage of AFP cases investigated within 48 hours, the target should be at least 80%. A percentage of AFP cases with two adequate stool specimens collected between 24 and 48 hours apart, and within 14 days of the onset, the target of at least 80%. Percentage of specimens arriving at the laboratory in a good condition, the target is at least of 80%. Percentage of specimens arriving at WHO-accredited laboratory within three days of being sent is at least 80%. And percentage of specimens for which laboratory results are sent within 28 days of the receipt, the target, at least 80%.
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Now this slide shows different type of surveillance. Remember that polio has a fecal-oral transmission. So detecting polio in sewage can be another way of find ongoing circulation. And this is what we call environmental surveillance. The surveillance involving testing sewage or other environmental samples for the presence of polio virus. Environmental surveillance often confirms wild polio virus infection in the absence of cases of paralysis. Systematic environmental sampling, for example, in Egypt, and Mumbai, India provide important supplementary surveillance data. Ad hoc environmental surveillance elsewhere, especially in polio-free regions, provide insight into the international spread of polio viruses.
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So, because of that, polio eradication looks for virus in environmental sampling sites across the world, as we see in this map. There are different number of sites in different countries to monitor the environmental sampling across the world. In the previous slide, we see the location of environmental surveillance around the globe. One of the particular interest of environment surveillance is in Afghanistan and Pakistan. In this slide, we see a map of areas between Afghanistan and Pakistan. You can see the symbol of people represent cases picked up by AFP surveillance, while the triangles show environmental surveillance. Each of the symbols are color-coded. This is because its polio cases, which was confirm, were genetically sequenced in the lab.
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It allow us to see which polio cases is closely related. Each of the same color represent case that closely related to each other. The blue cases are closely related to the other blue cases, and the red cases is also the same. And it is also true with the environmental samples which were collected and found positive and contained polio viruses. And from this map, we can see here that there were three key areas of transmission in this area. One is Peshawar and Nangarhar, another one is Baluchistan and Kandahar, and the third one is Karachi. And in some areas of transmission where we see environmental sample are positive, there were no AFP cases.
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But, it also means that we should worry also in this area, because it represent a high risk area for transmission.

Riris Adondo Ahmad, MD, MPH, PhD
Faculty of Medicine, Public Health and Nursing, Gadjah Mada University, Indonesia

The polio surveillance system is among the most effective and comprehensive global surveillance systems ever developed, both in terms of its reach and technical capacity. Now that you have heard about the complex workings and numerous steps undertaken by the polio surveillance system, think about the following questions;

  • Why is surveillance in hard to reach areas especially difficult?
  • Why it is even more important to maintain sensitive surveillance systems in these areas?

Share your thoughts in the discussion.

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