The risk factors of measles outbreak in Dollo zone Somali region, Ethiopia

INTRODUCTION

Measles is a highly contagious acute viral illness with the possibility of severe and dangerous complications.¹ Measles occurrence is related to urbanization because of high entry of migrants and high population density; cities have become important hubs for the spread of infectious diseases. Eleven countries including Ethiopia accounted for 66% of measles deaths in 2000.² However, regardless of efforts, measles outbreaks continue to occur even in countries which introduced measles mass vaccination as part of their national immunization programs, and globally an estimated 134,200 measles deaths were reported in 2015, mostly in low-income countries.³

Measles has persisted as one of the vaccine-preventable diseases causing major mortality and morbidity in developing countries.⁴ Several countries in sub-Saharan Africa, southern and central Asia have made enough progress to achieve Millennium Development Goal (MDG₄) Millennium Development Goals are eight goals which measurable targets and clear deadlines for improving the lives of most impoverished people leaders of 189 countries signed the historic millennium declaration at united nations submit in 2000 to meet this goal and eradicate poverty.⁵ The African region is a key player in the global fight against measles and has made tremendous progress in its effort to immunize children and to control the disease.⁶ Despite the accessibility of a safe and cost-effective vaccine, measles has remained endemic with persistent periodic outbreaks in the horn of Africa.⁷ The introduction of the measles enhanced control strategy, and mortality reduction goal has reduced mortality both developed and developing countries. In 2001, countries in the World Health Organization (WHO) African Region started applying the regional measles mortality reduction goal to reduce though increase of routine immunization, supplementary immunization, case-based surveillance and improving case management.⁸

In Ethiopia, the estimated measles incidence was 6.52 per 100,000 population in 2013 and 14.61 per 100,000 population in 2014.⁹ During 2010 and 2011 there were 9756 measles cases reported.¹⁰ Measles is a major cause of mortality in a complex emergency. Both a high vaccination coverage and high vaccine efficacy are required to prevent major epidemics of measles in complex emergencies.¹¹

Countries with a high measles load and inadequate financial resources are challenged with difficult decisions related to measles control.¹² The use of supplemental immunization and routine immunization in a marginalized population requires social mobilization which can be expensive.^13,14

In Ethiopia, about 1 million children were estimated to be unvaccinated, and 16% of the <5-year-old mortality has been attributed to vaccine-preventable diseases. Immunization is one of the national child survival strategies in the country the country targets is to achieve diphtheria-pertussis and tetanus (DPT₃)/measles vaccination coverage of 90%.¹⁴

Measles is one of Ethiopia’s priority diseases under surveillance, and it is immediately reportable. A confirmed measles outbreak was reported from Ethiopia Somali region from February to March 2016, during which a rumor of suspected measles was reported from Dhagaxbur Hospital Jarar Zone Somali region. The zonal hospital for Somali Regional Health Bureau and partners departed to this site with the objective of confirming the existence outbreak through laboratory investigation initiating preventive measure and formulate appropriate recommendations based on the result of the investigation.¹⁵

The measles outbreak intensified and affected all age groups shifting to younger to older ages.¹⁶ This study was aimed to find risk factors contributing to the measles outbreak in Dollo zone.

METHODS

Study area

The study was conducted in Dollo zone of the Somali region in Ethiopia. Dollo zone is the largest zone in the Somali region with an estimated population of 403,266 (Ethiopia Central Statistics Agency projection of 2018). The rural population is 86% and 85% lead a pastoral-nomadic lifestyle. Between 2016 and 2017 Dollo zone experienced an exceptional drought emergency mainly due to an underperforming rainy season. The subsequent years of drought lead to low yields in crops and pasture, and loss of livestock led to significant food insecurity which in turn led to high severe and moderate acute malnutrition in the population with <5-year-old children most affected. Furthermore, Dollo zone hosts internally displaced people with 48 sites with a total population of 89,694 which is at risk for outbreaks. The coverage of health and nutrition in Dollo zone insufficient and fails to meet the basic health care service. Admiratively the zone is divided into seven woredas, and all were affected by the measles outbreak.

Study design

We reviewed the measles cases line lists in Dollo zone from January 2017 to March 2018. There was a total of 771-line listed cases in 2017 and 326 line-listed in 2018. Measles case investigations on alerts were also reviewed, and also measles case-based surveillance from health facilities of Dollo zone were referred.

We reviewed the variables on the line list which included vaccination status, age, sex, treatment modality, date of onset the rash, date seen health facility, diagnosis, outcome (alive or dead), the location where the cases came from, contact history and travel history. Vaccination status of the woredas and zones were also reviewed the measles coverage in 2017.

The line lists and public health emergency management (PHEM) weekly report were cross-checked for completeness and consistency.

Laboratory investigations were done on 35 samples of first cases from three woredas, and they confirmed outbreak in the three districts of the zone. The samples were sent to the national measles laboratory. After confirming outbreak cases that were linked to confirmed cases within the district were considered as epidemiologically confirmed.

The Somali Regional Health Bureau formed a technical working group for the measles outbreak response, and the technical working group met daily. We reviewed the documents and presentations from the technical working group.

We reviewed the Health Management Information System (HMIS) data of the Somali region for the Expanded Program for Immunization (EPI) delivery service, and we also reviewed interventions done as long the outbreak going on the zone. There were several intervention activities done in the affected woredas of the zone, for example, mop-up vaccination, strengthened surveillance activities, enhancing routine immunization, proper case management and proper referral system.

Data analysis

We used Microsoft Excel to analyze the different variables of the line lists like age, sex, vaccination history, treatment modality, contact history, travel history, specimen collected and the onset of rash.

RESULTS

Despite the limitation 86% of the line lists were complete, and 92% of variables were complete to provide a conclusion.

Warder woreda reported the largest number of cases, 301/771 (39%) of the total cases, 192/771 (25%) of the cases were reported from Lehelow-yucub woreda while the lowest number of cases were reported from Galhamur and Daratole woredas 21/771 (2.72%) and 20/771 (2.5%) respectively (Table 1).

Warder Woreda reported 12/24 (50%) of the confirmed cases in Dollo zone, Danot woreda had 6/24 (25%) cases and Daratole woreda had 4/24 (17%) confirmed cases (Table 2).

A total of 1700/2682 (63.4%) children were vaccinated in the first quarter and second quarter 1633/2682 (61%) children were vaccinated. In 2017 the first and second quarter were better than a third and fourth quarter, and half of the children were unimmunized in 2017 (Table 3).

Danot woreda vaccinated the largest number of children 1191/1369 (87%) of the target children in Danot woreda while Warder Woreda vaccinated the lowest number of children 409/1265 (32%) of the target children in Warder Woreda (Table 4).

The age group, 15 years to 30 years, was most affected with 464/1097 (42.3%) cases. The second most affected age group were 5 years to 14 years which was 324/1097 (29.5%) while the lowest affected cases were reported age above 30-year age group were 21/1097 (2%) (Figure 1).

The largest number of cases 130/326 (40%) were reported from Warder woreda. The second largest number of cases were reported from Danot woreda which is 107/326 (33%) cases while least woreda was Daratole and reported 4/326 cases (1.23%) (Figure 2).

In 2017 among the 771 measles cases the majority 552 (71.5%) were from internally displaced people (IDPs) while the cases from host communities were 220/771 (28.5%).

DISCUSSION

We found that measles outbreaks were commonest in IDPs as they are susceptible and had a high population density that resulted in an increased risk of measles transmission and measles outbreaks. IDPs are circumstances characterized by inadequate or no vaccination of the displaced populations before their coming into the refugee camps.^17,18 In our review, we found that Dollo zone had a low routine immunization coverage of 52.3% in 2017 which made it vulnerable to a measles outbreak and most of the IDPs had no history of vaccination.

We found that the samples collected from Dollo zone in 2017and sent national laboratory confirmed the measles outbreak in Dollo zone similarly samples collected from Amara Region confirmed the measles outbreak from 2004 through 2014.⁷

We also found that the measles outbreak affected different age groups in Dollo zone and the most affected people were aged between 15 years and 30 years and most of the cases had no history of vaccination. A high percentage of unvaccinated children were affected by this outbreak. Being unvaccinated against measles was a risk factor for contracting measles in Zaka district Zimbabwe.¹⁹ The outbreak affected all age groups, which may show continuous low routine vaccine coverage over several years and the gathering of the susceptible population in the older age groups that may have led to the current outbreak.^8,20

We also found low awareness of the community for routine immunization. Awareness of the community for the immunization program increases the knowledge of mothers to bring health facilities to vaccine their children. Community conversation awareness is one of the strategies for social mobilization through creating a dialogue among a community member targeting at raising awareness and behavioral change.^21,22

We realized that cases were increasing and expanded to all kebeles of the districts in Dollo zone along the year and measles cases were reported most of the settlements similarly a review on measles situation in Ethiopia in past and present in 2003 showed that the number of measles cases reported were increased along that year.¹⁶

We also found that cases delayed to come health facilities for management, there was a time gap between the date seen at health facilities and date of disease onset and diseases spread and develops complications in the community.⁹

We recognize the limitation of incomplete of line lists and incomplete of variables in the line list, and some of the weeks there were no reports. Also, variables like the status of vaccination history were not complete in the line lists.

CONCLUSION

Dollo zone is at a high in risk of subsequent outbreaks with regards to continue transmission in all age group; low routine immunizations almost of the half of the children were unimmunized in 2017. We recommend conducting mass measles vaccination campaign that targets 6 months to 30 years old, to strengthen and increase routine immunization service, to enhance and increase on community awareness of routine immunization and strengthen surveillance detection in health facilities and community.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee Somali regional health bureau

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