An evaluation of the Acute Flaccid Paralysis surveillance system, Northern Uganda, 2012-2015

Introduction: On 24th November 2014, two cases of circulating vaccine-derived poliomyelitis were identified in South Sudan bordering Uganda to the north. The strains were isolated from two acute flaccid paralysis (AFP) cases. Poliomyelitis is an infectious disease, highly communicable and infected persons can spread the disease for up to six weeks. The last poliomyelitis case in Uganda was in 1996 and Uganda was declared poliomyelitis-free in 2006. However there was WPV importation from South Sudan 2009 and from Kenya in 2010 and 2011. We therefore need to assess the effectiveness of the AFP surveillance system in the districts bordering South Sudan in responding to the imminent threat of poliomyelitis. The AFP surveillance system should entail investigation of all AFP cases within 48h of paralysis onset followed by collection of two adequate stool samples within 14 days of onset. The two stool samples should be received at a WHO accredited lab within three days of being sent and results sent within 28 days of being received. The investigation is completed by 

following up the cases investigated 60 days after initial investigation.
Methods: We defined an AFP case as sudden onset of weakness and floppiness of any limb in a child <15 years or paralysis of a person of any age in whom poliomyelitis is suspected. We found cases by AFP case investigation forms from 2012 to 2015. We also cross referenced the cases analyzed by the laboratory with those found in the records. The districts involved were Amuru, Moyo, Kitgum, Lamwo, Adjumani, Koboko and Yumbe. We analyzed the data to show surveillance performance indicators such as annualized non-poliomyelitis AFP rate /100 000 children <15 years, percentage of AFP cases with two adequate stool specimens collected 24-48 hours apart and <=14 days after onset, percentage of specimens arriving at a WHO accredited laboratory within three days of being sent and percentage of specimens for which laboratory results sent within 28 days of receipt of specimens. These are WHO standard indicators and have been used in evaluations elsewhere (1, 2).

Discussion: The evaluation revealed that 88% of cases had received at least 3 poliomyelitis vaccine doses. Poliomyelitis immunization coverage is a critical indicator of poliomyelitis prevention efforts. The rationale is that if a sufficient number of people are vaccinated, then transmission can be interrupted and outbreaks can be prevented from occurring. In northern Nigeria between 2003 and 2004, there was a suspension of all immunization activities because the locals rumored a link between the immunization and infertility and the human immunodeficiency virus (3). The drop in immunization coverage created a gap in the herd immunity that was insufficient to interrupt transmission which led to several poliomyelitis outbreaks (4). Nigeria has in fact remained on the list of vulnerable countries at risk of importation of poliomyelitis (5). The poliomyelitis endgame requires that every last child is fully vaccinated against poliomyelitis. Routine immunization in these districts should be fortified with house to house and extensive house to house and child to child mop-up immunization campaigns of all children <5 years to ensure 100% immunization coverage.
Another indicator of the efficiency of poliomyelitis surveil- lance is the annualized non-polio AFP rate of >1 /100,000 children <15. It refers to the incidence of AFP due to illnesses other than polio. In 2012, Adjumani and Moyo districts had an annualized non-Poliomyelitis AFP rate less than 1/100,000 children under 15 years. By 2015, all districts but Kitgum had annualized non-Poliomyelitis AFP rates ≥1/100,000 children <15 years.
This implies that there has been a steady increase

in the effective- ness poliomyelitis surveillance in the districts over the years. In this evaluation, none of the forms were filled for date of 60-day follow up and findings at 60-day follow up. This implies that while district surveillance focal persons make an effort to investigate AFP cases, there is reluctance to follow up the cases after collection and delivery of stool specimens at the lab. A distinguishing feature of paralytic poliomyelitis is that an infected person remains a carrier for several weeks (6) and paralysis could persist even after 60 days (7). The reluctance of surveillance personnel in following up cases after 60 days might be because they don’t see the need after they receive negative results from the lab. However the AFP cases could indicate outbreaks of paralytic neurological illnesses (such as Guillain-Barre syndrome, transverse myelitis, or tumors) among children <15 years (8) in those districts.
Koboko, Lamwo and Moyo performed poorly when it came to timely investigation of the AFP cases. In Lamwo and Moyo, most of the stool specimens were received at the lab after more than 3 days of being sent. On the roadmap leading to the eradication of poliomyelitis in the Americas, from 1992 until eradication, ≥80% of AFP cases were investigated within 48hours of notification (9). Also, the pro- portion of with adequate stool specimens collected gradually in- creased and consequently the number of wild poliomyelitis viruses reduced. The Ministry of Health should lobby for resources to be given to surveillance focal persons on delivery of stool samples that will ensure that AFP cases are investigated, the samples collected and received on time at the lab