Global measles control has been extremely effective. Following the implementation of the 2001 World Health Organization (WHO) member states goal of 50% measles mortality reduction by 2005, an estimated 60% reduction in measles-associated mortality was achieved worldwide, with a 75% reduction in the African region (Masresha et al., 2009; Goodson et al., 2011; Getahun et al., 2017; Asmare et al., 2022). Before the introduction of measles vaccination in Africa, measles was primarily a disease affecting young children, and 1 million cases were reported annually. In urban areas, measles epidemics occurred every 1 to 2 years, and the median age of cases was 1.5 to 2.5 years; in rural areas, outbreaks occurred less frequently, and the median age was 2.5 to 5.0 years (Goodson et al., 2011).

Ethiopia included measles vaccination in its routine extended program of immunization (EPI) in 1980, with the first dose administered at 9 months of age (Getahun et al., 2017). The overall immunization coverage in Ethiopia was 38.7, 36.55, 51.8, 67.1 and 66.9% for 2000, 2005, 2011, 2016 and 2019, respectively (Asmare et al., 2022). In 2013, an estimated 21.5 million children were not immunized against measles at the age of nine months. More than 60% were from India (6.4 million), Nigeria (2.7 million), Pakistan (1.7 million), Ethiopia (1.1 million), Indonesia (0.7 million), and the Democratic Republic of the Congo (0.7 million). More than 70% of global measles-related deaths occurred in these six countries in 2013, indicating that developing countries were the most affected (Wolters et al., 2017). Although vaccination coverage in Ethiopia is increasing year after year, the country continues to report a higher number of measles cases and outbreaks in all regional states and city administrations.

According to the WHO, Ethiopia is experiencing an ongoing measles outbreak, having reported over 14,000 confirmed cases in 2014 alone (World Health Assembly, 65. (‎2012), and being one of the world countries that experienced large outbreaks in 2009 and 2010, according to the CDC report (Minal et al, 2016). Measles is one of Ethiopia's nationally immediately notifiable diseases (Munira et al., 2018), and all health facilities (private and public) are required to report cases to the next level public health agency using the case definitions outlined earlier. Clinicians (internists, general practitioners, nurses, and health officers) reported suspected measles cases to the Ethiopian Public Health Institute for laboratory analysis using a case-based reporting form (Masresha et al., 2009).

The Ethiopian Public Health Institute is mandated by ministerial council regulations to conduct surveillance and laboratory investigations on epidemic-prone diseases such as measles (Mitiku et al., 2011). The aim of the measles case-based surveillance report analysis is to assess the trend of reporting measles cases, measure the positivity rate of measles samples, identify the age group most affected, and provide evidence for decision-makers.

Measles surveillance data was analyzed from the Afar region. Afar is a regional state in Ethiopia. It is Ethiopia's lowest point and one of the lowest in Africa. Afar, the coordinates are 14° 7' 48" N latitude and 40° 8' 24" E longitude.

The region is 1600 m above sea level, has a total area of 72,053 km², and is divided into five zones. Afar Regional State is in northeast Ethiopia, bordered by Eritrea to the north and northeast and Djibouti to the east (Figure 1). The total population of the Afar region was estimated to be 1.812 million (2017), with 811,776 females and 1009,284 males. Afar is one of four classified regions. Arc Geographic Information System (GIS) version 10.2 was used to depict the study area.

A retrospective measles case-based surveillance data record review was conducted from 2013 to 2017, and the data were extracted from the national measles and polio laboratory. Microsoft Excel was used for cross-sectional descriptive data analysis by time, place, and person variables and the result were presented in tables and graphs.

Data was cleared and checked for duplication using the patient's name, gender, age, residence area, date of onset, date seen at the health facility, and date of sample collection. Age, gender, year of the report, IgM result, and vaccination status analysis were used to categorize the data. Suspected measles case was tested according to the testing algorism for measles and rubella suspected cases as shown in Figure 2. A positive RT-PCR result or positive IgM result in patients with rash and with a history of travel in a measles endemic area or with an epidemiological link to a confirmed case are diagnostic for measles infection. Sero conversion, or a fourfold increase of measles IgM in a patient with rash and no history of recent MMR vaccination, is also diagnostic for measles. Negative results by RT-PCR and negative IgM-class antibody detection may not be sufficient to rule out measles infection in some cases, particularly if the specimen for PCR was collected later than 7 days after symptom onset (Fatiregun  et al, 2015).

Suspected measles is defined as any person with fever and a maculopapular (no vesicular) generalized rash and cough, coryza or conjunctivitis (red eyes) or any person in whom a clinician suspects measles: According to the national guideline (Munira et al., 2018), we further classified the suspected measles cases collected through surveillance into the following categories.

Laboratory confirmed cases are suspected measles cases with laboratory results that show measles IgM positivity. Those who live in the same or a nearby district as a laboratory-confirmed case where there is a likelihood of transmission; the onset of the rash of the two cases occurring within 30 days of one another; and are linked (in place, person, and time) to the laboratory-confirmed case are considered to be epidemiologically linked cases of measles.

A discarded measles case is a suspected measles case that lacks serologic evidence of a measles virus infection after an adequate investigation that includes a blood specimen collected within the appropriate time frame. A person who has received one dose of MCV1 is considered to be immunized against measles antigen.

If there are three or more measles laboratory-confirmed cases, there is  an  outbreak  of  measles;  and  if  there  are  five  or  more suspected measles cases, there is a suspected outbreak of measles for a particular district for the last four weeks, according to the national measles guideline.

In the period between 2013 and 2017, a total of 400 cases of measles were documented throughout the region,  according   to   case-based   laboratory   data  for surveillance. Male and female measles cases were nearly equally distributed; 52.2% (209) of them were men, and 47.8% (191) were women. The median age of the cases was 6 years old, with ages ranging from 1 month to 60 years old.

Among the total cases, 222 (55.5%) were laboratory-confirmed measles cases, 146 (36.5%) were negative for measles IgM, 11 (2.75%) were equivocal cases, and the remaining  22 (5.5%)  had  no  lab  results.  It is difficult to find the result for rubella virus-specific IgM antibody, another rash febrile illness, among the total 157 measles IgM negatives and equivocal cases. Children 5-14 years old had the highest proportion of tested people (37.5%), followed by children 0-4 years old (36.8%). Measles confirmed cases increased up to the age of 15 years and then decreased after that (Figure 3).

Of the total number of measles case-based laboratory data, 317 (79.25%) lacked information on their immunization status, 27 (6.75%) were immunized, and the remaining 56 (14%) were not immunized (Table 1). Sample collection peaked in 2015 with 161  and  in  2017 with 34. (Table 1). The year with the fewest positives (9) was in 2017, and the highest positive proportion (73.9%) was 2015 (Table 1).

Out of all district case-based laboratory data, Dubti district has the highest 36 (9%), and Dalule and Koneba districts have the fewest sample numbers 1 (0.3%), each among 34 districts. In the last five years, 58 (14.5%) most districts were blank, as shown in Figure 4. The highest laboratory sample tested throughout 2015 was 161 (40.25%), and the highest sample tested in July was 28 (7%), as seen in Figure 5. As indicated in Table 1, the year  2017  had  the  smallest  sample  tested  34 (8.5%), among the samples recorded over the previous five years. In July, there was just one sample tested.

The data analysis had the following limitations: first, the data was only related to laboratory-confirmed measles data, with little emphasis on clinically confirmed and epidemiologically linked cases detailed as laboratory data. Second, there is no information on the clinical signs and symptoms of the cases, such as fever, maculopapular rash, diarrhea, and vomiting, as well as complications such as ear and sinus infection, persistent diarrhea, and pneumonia. Third, there are no measles indicator variables by administrative, such as expected and reported non-measles febrile rash rate cases by zone and district, which are required for determining the incidence and annualized non-measles febrile rash rate. Finally, there is no information in the laboratory data on rubella IgM results for cases other than measles.

Measles is still a major health problem in this region, primarily affecting children aged 5 to 14. The number of laboratory-confirmed measles cases varies by year and season. Most children have unknown  vaccination  status, and the sample tested in different years is different, possibly due to health system improvement or a lack of sensitivity in the surveillance system in health facilities and district health offices. The names of health facilities and districts were inconsistent, and districts were not filled, as were measles indicators such as NMFRR, incident rate, the district expected and reported measles, total population, specimen condition, and week of report, all of which are critical indicators in the database system.

(1) To increase the region's measles vaccination rate, FMOH should execute supplemental immunization activity (SIA) in partnership with EPHI and other partners.

(2) The surveillance efforts need to be improved for the specificity of reporting suspected measles in all hierarchies, the completeness of variables, and the early detection of cases.

(3) Yearly review meeting that is held regularly to discuss vaccine-preventable disease

(4) Enhanced database administration for simpler analysis.

The authors appreciate the contribution  of  the  Ethiopian Public Health Institute vaccine preventable team for technical support of the National Measles Surveillance Program and  all  health  care  workers  involved  in  case identification and sample collection, and patients who gave blood at all health institutions in Afar Region, Ethiopia.

The authors have not declared any conflict of interests.