Polio Outbreak Investigation and Response in Somalia, 2013
Polio Outbreak Investigation and Response in Somalia, 2013
Raoul Kamadjeu 2
Abdirahman Mahamud 0
Jenna Webeck 0
Marie Therese Baranyikwa 1
Anirban Chatterjee 1
Yassin Nur Bile 3
Julianne Birungi 0
Chukwuma Mbaeyi 0
Abraham Mulugeta 2
0 Global Immunization Division, Centers for Disease Control and Prevention , Atlanta , Georgia
1 United Nations Children's Fund Somalia , Nairobi , Kenya
2 Somalia Liaison, World Health Organization
3 Health Directorate, Somalia Ministry of Human Development and Public Services , Mogadishu
Background. For >2 decades, conflicts and recurrent natural disasters have maintained Somalia in a chronic humanitarian crisis. For nearly 5 years, 1 million children <10 years have not had access to lifesaving health services, including vaccination, resulting in the accumulation by 2012 of the largest geographically concentrated cohort of unvaccinated children in the world. This article reviews the epidemiology, risk, and program response to what is now known as the 2013 wild poliovirus (WPV) outbreak in Somalia and highlights the challenges that the program will face in making Somalia free of polio once again. Methods. A case of acute flaccid paralysis (AFP) was defined as a child <15 years of age with sudden onset of fever and paralysis. Polio cases were defined as AFP cases with stool specimens positive for WPV. Results. From 9 May to 31 December 2013, 189 cases of WPV type 1 (WPV1) were reported from 46 districts of Somalia; 42% were from Banadir region (Mogadishu), 60% were males, and 93% were <5 years of age. All Somalian polio cases belonged to cluster N5A, which is known to have been circulating in northern Nigeria since 2011. In response to the outbreak, 8 supplementary immunization activities were conducted with oral polio vaccine (OPV; trivalent OPV was used initially, followed subsequently by bivalent OPV) targeting various age groups, including children aged <5 years, children aged <10 years, and individuals of any age. Conclusions. The current polio outbreak erupted after a polio-free period of >6 years (the last case was reported in March 2007). Somalia interrupted indigenous WPV transmission in 2002, was removed from the list of polioendemic countries a year later, and has since demonstrated its ability to control polio outbreaks resulting from importation. This outbreak reiterates that the threat of large polio outbreaks resulting from WPV importation will remain constant unless polio transmission is interrupted in the remaining polio-endemic countries.
Somalia; poliomyelitis eradication; outbreak; wild poliovirus; horn of Africa
Somalia is one of the poorest and most volatile
countries in the world. More than 2 decades of civil unrest
have left basic healthcare infrastructure in a state of
despair; coverage for basic public health interventions
is low, and maternal and child mortality are among the
highest in the world . The country is divided into 4
operational zones (North-East, North-West, South, and
Central) and subnational entities extending to regions
and districts. Persistent insecurity severely restricts
access by international humanitarian staff to most
areas of South and Central Somalia to provide lifesaving
Despite numerous challenges, the Somalia polio
program has demonstrated its ability to successfully
implement polio eradication strategies. Indigenous wild
poliovirus (WPV) transmission was interrupted in Somalia
in 2002, 5 years after the country initiated polio
eradication activities. However, an initial polio outbreak
resulting from importation of WPV type 1 (WPV1) swept the
country from 2005 to 2007 (the last case had an onset
date of 25 March 2007), claiming >229 cases of paralytic
polio. The current outbreak (in 2013) started in May
2013, when a case of WPV1 was reported from a
32month-old girl in the Mogadishu area (Hamar Jajab
district); the date of paralysis onset was 18 April 2013.
The outbreak soon expanded to all of Mogadishu’s 16
districts, with secondary spread to other areas of South and
Central Somalia. As of 31 December 2013, 189 cases of WPV1
were notified from 46 of 110 districts of the country, mostly
from the security compromised areas of South and Central
Somalia. With 48% of all polio cases reported globally in
2013, the current polio outbreak in Somalia threatens the World
Health Assembly (WHA)–endorsed Polio Eradication and
Endgame Strategic Plan 2013–2018 objective of stopping all polio
transmission globally by the end of 2014 . This is a strong
reminder of the persistent risk of WPV importation and
circulation in security-compromised areas of the world as long as polio
eradication is not completed.
We describe the 2013 polio outbreak in Somalia (data are
current as of 31 December 2013), with emphasis on the
epidemiology, risk factors, response activities, and challenges the
program will face in making Somalia free of polio once again.
Setting and Population
Somalia has a population estimated at 10 million people . The
country shares land borders with Kenya, Ethiopia, and Djibouti
and a sea border with Yemen. Children aged <15 years make up
44% of the total population . Political instability, insecurity,
and recurrent natural disasters are major drivers of population
movements inside the country; in 2013, an estimated 1.2 million
internally displaced persons were reported within the country
, the majority of whom were in Mogadishu, the capital and
most populated city in the country. In addition to the 4
operational zones, Somalia is divided into 19 regions and 110
districts. With a healthcare system entirely destroyed during >2
decades of instability, the country has some of the lowest health
indicators in the world: in 2012, the mortality rate among
children aged <5 years was 180 deaths/1000 . The reported
national coverage with 3 doses of oral polio vaccine (OPV3)
through routine immunization has been historically low and
was <50% in 2012 .
Acute Flaccid Paralysis (AFP) Surveillance
and Case Identification
Cases of polio are identified through the AFP surveillance
system. The polio surveillance network in Somalia consists of >190
national surveillance officers located at zonal, regional, and
district levels, with technical support from international staff from
the World Health Organization (WHO) and the United Nations
Children’s Fund (UNICEF). National staff often have access to
security-compromised areas of the country where international
staffs have limited access. Surveillance officers visit on average
500 reporting sites, distributed across the country, on a weekly
basis to actively search for cases of AFP. The surveillance
network also extends to communities, through traditional healers,
private pharmacies, vaccinators, and village polio volunteers. A
case of AFP is defined as a child aged <15 years with sudden
onset of fever and paralysis. All AFP cases are investigated
and stool samples collected by national polio workers according
to AFP surveillance guidelines . For each AFP case, 3
additional stool samples are collected from contacts; an AFP case
contact is defined as anyone of similar age to the AFP case
who resides in the same household or neighborhood. Stool
samples collected from AFP cases and contacts are sent to the Kenya
Institute of Medical Research (KEMRI) polio laboratory for
virus isolation, typing, and intratypic differentiation, using the
WHO standard polio testing procedures . WPV strains
isolated by the KEMRI polio laboratory were sent to the Centers
for Disease Control and Prevention (Atlanta, GA) or the
National Institute for Communicable Diseases (Johannesburg,
South Africa) for genetic sequencing. Based on the outcome
of the laboratory investigation, AFP cases are classified as either
confirmed polio cases or discarded as cases of
non–polioassociated AFP. Additional significant potential laboratory
outcomes include classification of virus isolates as Sabin-like virus
or vaccine-derived poliovirus (VDPV).
Data Collection and Analysis
Demographic, clinical, and laboratory information on AFP and
confirmed polio cases are recorded in the AFP surveillance
database. Analysis of AFP data is conducted by the program on a
regular basis to monitor AFP surveillance performance. The
AFP database is shared on a weekly basis with the Polio
Eradication Initiative partnership for regional and global reporting.
Additional sources of information for this report include
supplementary immunization activity (SIA) data, documents
such as action plans, and monitoring reports.
As of 31 December 2013, stool samples from 545 AFP cases
and 1761 contacts were collected and shipped to the KEMRI
polio laboratory for WPV isolation.
Since 2000, the country has exceeded the WHO-established
minimum AFP reporting rate of 2 non–polio-associated AFP
cases per 100 000 children aged <15 years and has maintained
key AFP surveillance indicators above certification standards at
the national level .
Detection of the 2013 WPV Outbreak
On 9 May 2013, a 32-month-old girl from Hamar Jabjab district
in Mogadishu was confirmed as having WPV1 infection by the
KEMRI polio referral laboratory in Nairobi. The date of onset of
paralysis was on 18 April 2013 (epidemiology week 15). The
child and her family reported no history of travel outside
Mogadishu prior to onset of paralysis. In addition, 3 close contacts of
the index case were confirmed to have asymptomatic WPV1
infection. A detailed case investigation was conducted
immediately following the confirmation of the index case.
As of 31 December 2013, 189 polio cases were confirmed
from 46 districts of the South and Central zones and 1 district
in North-East zone. All WPV1 isolated in Somalia belong
to cluster N5A; known to have been circulating in northern
Nigeria since 2011.
Initially limited to the capital Mogadishu, the outbreak
quickly spread to other districts of the South and Central
zones, with an average incidence of 7 cases per week during
epidemiology weeks 15–39 (Figure 1). Early in the outbreak
(weeks 18–23), Mogadishu experienced intense WPV
transmission, with an average incidence of 8 cases per week during the
peak period; at the time of writing, the region had accounted for
38% of all reported WPV cases (70 cases). Overall, the WPV
incidence decreased over the last 8 weeks to <3 cases per week,
from a high of 12 cases per week at the height of the outbreak.
No new case was reported from Mogadishu for >25 consecutive
weeks. The outbreak also acquired international status; at the
time of this report, 14 WPV1 cases had been reported in
northeastern Kenya and 9 cases had been reported in eastern Ethiopia,
all genetically linked to the WPV1 from Somalia.
As a result of the outbreak, surveillance activities were
strengthened throughout the country. Active search for AFP cases through
the extensive network of polio officers was intensified at reporting
sites and within the communities, resulting in a marked
improvement of the key AFP surveillance indicators at all levels.
Characteristics of WPV Cases
The average age of WPV cases was 2.6 years (range, 2 months to
27 years); 175 of the 189 cases (93%) notified at the time of this
report were <5 years of age. One WPV case was >15 years of age.
The occurrence of WPV in a 27-year-old adult was notable in
this outbreak but remained an isolated occurrence. The
majority of cases were male (60%). The immunity profile of cases
clearly indicated that failure to be vaccinated was the major
risk for WPV infection in this outbreak; 55% of all WPV cases
had never received OPV (so called 0-dose individuals), and
almost 80% were undervaccinated (ie, they had received ≤3 doses
WPV and District Accessibility for SIAs
For >4 years, an estimated 1 million children aged <10 years
could not be reached with OPV in some districts of South
and Central Somalia because of the ban imposed on
immunization by some local antigovernment elements. Of the 109
districts listed in the AFP database, 27 are currently completely
inaccessible for SIAs, while 12 are partially accessible (SIAs
can be conducted in limited localities within the districts;
Figure 2). Analysis of the WPV incidence by district accessibility
status (Figure 2) shows a progressive extension of the outbreak
from accessible to inaccessible or partially accessible districts;
38% of the 113 cases reported in the first 3 months of the
outbreak were from accessible districts, mostly in the Banadir
region (Mogadishu); 0.7% of the 71 cases reported during
months 4–6 of the outbreak were from accessible districts.
The first immunization response using trivalent OPV and
targeting 360 000 children <5 years of age in the 16 districts of
Mogadishu and in 1 district of Lower Shabelle (Afgoi district)
was conducted within a week of notification of the index case.
A 6-month emergency response plan was finalized within 2
weeks of notification of the first WPV case. The 6-month
emergency response plan focused on the known and most
effective strategies to control this importation-related outbreak,
notably strong surveillance, large-scale polio SIAs with OPV
implemented as soon as possible after notification of the first
case and continued on a large scale, and targeted SIAs using
bivalent OPV until the outbreak was stopped.
To rapidly build high population immunity and to reduce the
risk of spread of the virus, the 6-month emergency response
plan adopted a flexible approach for the selection geographic
size and target age group for SIA rounds. The capacity to
rapidly respond with SIAs or subnational campaigns should any
currently inaccessible area become accessible for immunization
activities was also factored into the emergency response plan.
Overall, 8 rounds of polio SIAs (one of which used trivalent
OPV) were conducted in all accessible districts of Somalia,
targeting between 3 million and 8.5 million persons from various
age groups (children aged <5 years, children aged <10 years, and
individuals of all ages). To account for mobile and displaced
populations, close to 300 special transit vaccination posts,
each functioning as a cordon sanitaire, were established at
main transit points within accessible areas, reaching on average
74 000 persons per week.
For the first time in >5 years, independent monitoring (IM)
of SIAs was reintroduced and progressively expanded from 16
districts during initial activities to 49 districts at the time of
this report. The independent monitoring teams assessed,
through finger marking, the vaccination status of 8811–34 330
children aged <5 years from 16 to 49 districts of Somalia.
Overall, the coverage varied from 72% to 82%. The main reasons for
missing children were unavailability of the child or parent and
team performance issues (eg, teams did not revisit houses or
houses were not visited). Overall, 77% of the households were
aware of the campaign. Review of independent monitoring
findings (data not shown) confirmed an increase in the number of
children reached during successive SIA rounds in the majority
Polio control and coordination rooms were established in Nairobi
and Mogadishu to improve the efficiency of outbreak response
operations. The control rooms improved the overall coordination
of the outbreak response operation across partner
organizations by maximizing communication, reducing bottlenecks,
and streamlining reporting activities. Situation reports on the
outbreak were shared with partners on a weekly basis through
polio control rooms.
Communication and Social Mobilization
The intense nature of the immunization response (1 round of
SIAs every 3–4 weeks), variation by SIA round in the age group
targeted, vaccination of adults in some rounds, and the ban on
immunization by antigovernment groups required innovative
communication approaches to respond to this outbreak. An
outbreak communication plan was developed to address these
challenges. The plan focused on 5 main strategies: advocacy,
mass media/promotion, community engagement/social
mobilization, behavior change/participatory communication, and
capacity building. As a consequence of intensified communication
and social mobilization activities, the adherence of the Somali
population to polio activities has been secured. A high level of
awareness and a low level of OPV refusal were reported during
SIAs (unpublished data, 2013).
As of 31 December 2013, 189 cases of WPV1 have been
reported in Somalia, the first outbreak after a polio-free period of >6
The current polio outbreak in Somalia threatens the
WHAendorsed objective of stopping all polio transmission globally by
the end of 2014 . The outbreak also highlights the
susceptibility of security-compromised countries with weak healthcare
systems and low population immunity to WPV importation
and sustained transmission as long as polio eradication is not
At the beginning of the current outbreak, WPV outbreak risk
assessments conducted using existing polio risk assessment
methods on a regular basis by the program [8–10] placed Somalia
at its worst immunity profile within the last 5 years. The risk of
WPV importation in Somalia is compounded by several factors:
(1) for >4 years, an estimated half million children aged <5 years
residing in 39 districts of South and Central Somalia have
not been reached with large-scale immunization because of a
ban on immunization activities imposed by antigovernment
elements; (2) provision of routine immunization services is
suboptimal as a result of >2 decades of civil unrest; and (3)
persistent insecurity in most parts of the country limits the ability of
polio officers to access key locations to support, monitor, or
evaluate the implementation of SIAs and other polio
The detection of circulating VDPV (cVDPV) from 2008 to
2013, mostly in South and Central zones of Somalia, signaled
a permissive environment, ripe for WPV importation and
circulation. Considering this context, the current outbreak did not
come as a surprise; in fact, an explosive and protracted outbreak
was the most likely scenario predicted in the case of WPV
importation. The rapid expansion of the outbreak nationally to other
districts and internationally to Kenya and Ethiopia confirmed
this original fear.
Three months into the course of the outbreak, an outbreak
response assessment was conducted to evaluate whether the
quality and adequacy of outbreak response activities were
sufficient to interrupt polio transmission within 6 months of
detection of the first case, as per WHA-established standards.
The findings of the assessment included several observations:
the initial response to the outbreak was fast and aggressive;
initial investigation and activation of local response were done
within 72 hours of index case confirmation; and the first round
of the SIA response was implemented within 5 days of
notification of the index case in Banadir, well within the WHA
Resolution 59.1 outbreak response requirements in polio-free countries
. This initial response was followed by intensive rounds of SIAs
at 3–4-week intervals, targeting various age groups, including
adults, in all accessible districts of Somalia. The outbreak
response was facilitated by the commitment and support of
local governments, United Nations agencies, local communities,
and partner organizations, including nongovernmental
organizations, and the adequate and timely availability of logistical
and financial resources.
A marked reduction of the incidence of WPV in accessible
districts, particularly in Banadir, the epicenter of the outbreak,
where no case has been reported for >25 consecutive weeks,
indicates a positive impact of the outbreak response activities. The
focus of the outbreak has shifted to inaccessible areas of the
country. The recent detection of 2 WPV1 cases in North-East
zone confirms the persistent risk of reimportation to
poliofree areas of the country.
The current accessibility situation in Somalia, notably, the
limitation in the movement of polio staff in inaccessible
districts, the inability of international staff to access most parts
of the country for key monitoring activities, and the logistical
challenges sometimes associated with shipment of stool samples
from the field to the polio reference laboratory, all continue to
impact the detection of WPV in inaccessible and remote places
of South and Central Somalia.
In summary, the 2013 Somalia polio outbreak demonstrates
the fragility of the achievements of the polio eradication
initiative and is a potent reminder of the urgent need to complete
polio eradication. The inability to mount an appropriate
outbreak response in inaccessible districts poses a threat to the
control of the outbreak, with the risk of continued exportation of
WPV from inaccessible to accessible districts. Countries facing
similar challenges or falling into instability, with rapid
deterioration of healthcare systems and immunization service delivery,
become at high risk of WPV reintroduction and sustained
transmission, which will further delay the noble objective of
timely eradication of polio. Somalia has demonstrated its ability
to effectively control polio outbreaks in the past and has made
significant progress in the control of the current outbreak;
adherence to high-quality polio eradication strategies, consistent
support of polio eradication partners, persistent research and
implementation of innovative strategies to address the large
population immunity gap, and a hope of improvement of the
political situation in the country will be key determinants of
Acknowledgments. We thank the polio eradication officers in Somalia
who have been fighting polio, effortlessly, since 1997, sometimes at the cost
of their life, for their work and dedication; and local NGOs and partners of
polio eradication in Somalia.
All authors have contributed to this manuscript in ways that comply with
the ICMJE authorship criteria and have read and approved the final version
of the manuscript.
Financial support. This work was supported by the Polio Eradication
Initiative, which is spearheaded by the World Health Organization; the
US Centers for Disease Control and Prevention, the United Nation
Children’s Fund, Rotary International, and the Bill and Melinda Gate Foundation.
Potential conflicts of interest. All authors: No reported conflicts.
Supplement sponsorship. This article is part of a supplement entitled
“The Final Phase of Polio Eradication and Endgame Strategies for the
Post-Eradication Era,” which was sponsored by the Centers for Disease
Control and Prevention.
All authors have submitted the ICMJE Form for Disclosure of Potential
Conflicts of Interest. Conflicts that the editors consider relevant to the
content of the manuscript have been disclosed.
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