Study Area and Period
The study was conducted in Siraro District, West Arsi Zone, Oromia Region. This area is under the catchment of Biftu and Shasha Health centers. Siraro District is located in the Great Rift Valley of Southern, Oromia Region, Ethiopia.The administrative center of Siraro District is Loke, which is located about 304 kilometers to the South of Addis Ababa and 54 kilometers way from Shashamanne (Zonal town). The district borders Sidama Region to the southeast, Walayita zone to the southwest, Hadiya zone to the west, Halaba special zone to the north, and Shala District to the east (Fig. 1). Demographically speaking, a total of 207,541 people in which 10, 7921 were females and 30,410 were under-five children inhabit the District. The district is administratively organized into 28 rural kebeles, and 4 urban kebeles. The District had one primary hospital, 6 health centers (HCs), and 28 health posts (HPs) with primary health care coverage of 85.7% reported by Siraro district. The climate is 90% desertic. The mean annual temperature is between 18.5 to 25.5 degrees centigrade. The district generally lays at an altitude between 1500 and 2075 meters above sea level. These above districts' weather conditions, altitude, and temperature favor breeding of disease-causing vector-like anopheles mosquitoes. The district covers an area of 1312.855 square kilometers. The annual average rainfall is about 1650 milliliters, but inadequate and seasonal between 900 to 1500 milliliters per year. We conducted this study from 16 June to 03 August 2021.
Study Design
We used a community-based unmatched case-control study design with a 1:1 ratio of case and control to identify risk factors and cross-sectional study design to describe in terms of person,place and time for the occurrences of the malaria outbreak in the district.
Population
Source Population
All populations living in the Siraro district of the West Arsi Zone were the source population for this study.
Study Population
All populations of Siraro district where Malaria outbreak occurred were the study population
Study Subject
Case
Any person living in Siraro district during the study period with fever or fever with headache, rigor, back pain, chills, sweats, myalgia, nausea, vomiting and confirmed positive by microscopy or Rapid Diagnostic Test (RDT) for Plasmodium parasites and who agreed to participate in the study were included in the study.
Controls
Any resident of Siraro district during the study period who is a neighbor to a case and who did not develop signs and symptoms of malaria and confirmed negative by microscopy or Rapid Diagnostic Test (RDT) for plasmodium parasites.
Eligibility criteria
Inclusion Criteria
For cases
Any resident of the Siraro district where malaria outbreak occurred and who had symptoms of malaria and confirmed positive by microscopy or Rapid Diagnostic Test (RDT) for Plasmodium parasites and agree to participate were included from the study.
For controls
Any resident of Siraro district where malaria outbreak occurred, neighbor to a case and who did not develop signs and symptoms or free from malaria disease in the house and confirmed negative by microscopy or Rapid Diagnostic Test (RDT) for Plasmodium parasites and agree to participate.
Exclusion Criteria
For cases
Any resident of Siraro district where malaria outbreak occurred, who had symptoms of malaria and confirmed positive by microscopy or Rapid Diagnostic Test (RDT) for Plasmodium parasites but who refused to participate were excluded from the study.
For controls
Those who refused to participate, were unavailable during the study period, and did not fulfill inclusion criteria were excluded from the study.
Variables in the study
Dependent variables
Presence of malaria infection (case & control).
The independent variables
Socio-demographic factors
Age, sex, occupation, religion, ethnicity, and educational status.
Environmental factors
Plant water pools, open deep well, broken materials, and stagnant water.
Housing condition factors
House screen, sprayed and bed net in household.
Knowledge related factors
Way of transmission, know symptoms of malaria, and way of prevention.
Operational, case definitions and measurements
Malaria
A disease in an individual in which the presence of Plasmodium parasites in blood has been confirmed.
Resident
Individuals (workers) who had been living for more than 3 months and are normal residents of the study area.
Cases
Any person with fever or fever with headache, rigor, back pain, chills, sweats, myalgia, nausea, vomiting and confirmed positive by microscopy or RDT for plasmodium parasites.
Controls
Any person who is a neighbor to a case and who did not develop symptoms of malaria.
Suspected
Patient with fever or history of fever in the last 48 hours and who lives in malaria-endemic areas or has a history of travel within the past 30 days to malaria-endemic areas.
Probable
Any person with fever and one or more major signs such as headache, rigor, back pain, chills, sweats, myalgia, nausea, and vomiting are diagnosed clinically as malaria.
Confirmed
Any suspected case that is confirmed by microscopy or RDT for plasmodium parasites.
Line-List
Registrations of cases by place, person, and time.
Knowledgeable
If respondents answer > 60% correctly knowledge-related questions, then they are known to that question.
Not Knowledgeable
If respondents answer ≤ 60% correctly knowledge-related questions, then they are not known to that question.
Sample size determination and sampling procedures
Sample size determination
For descriptive epidemiology
Malaria was defined and identified as an acute febrile illness with blood smear positive for malaria in the Siraro District outbreak in 2021. During this outbreak investigation, the number of malaria cases and deaths were collected from health facilities on a daily and weekly basis. The magnitude of this outbreak was described by age, sex, and kebele, weekly, monthly, slide positivity rate was calculated as those positive for malaria among the total 183 confirmed cases examined from line list reported of Siraro district.
For analytical epidemiology: The sample size for both cases and control was recruited by using a 1: 1 ratio of case and control. The assumption taken from a previous study indicates that the proportion of controls exposed was 55% for a power of 80% with an odds ratio (OR) of 2.90. (9). The sample size which was taken from each group was determined by Epi-Info version 7.2.4.0 and the final sample size generated was 74 malaria cases and 74 community controls total of 148 study participants. The significance of risk factors for the outbreak was determined through multivariate analysis by calculating Odds Ratio (OR) and 95% Confidence Interval (CI).
Sampling technique and procedures
The simple random sampling method was used at the places where the outbreak occurred and was selected randomly confirmed cases with the highest caseloads and community control interviewed from two affected kebeles.
Data collection method, tools, and procedures
Data was collected by using a structured questionnaire and by reviewing secondary data at the district after discussing with relevant bodies (task force), review of weekly Public Health Emergency Management (PHEM) reports at different levels ( zone health department, District health office, and Health facilities), health extension workers (HEWs), review on available data from line list, visiting of the affected village and interview of community members (patients) to collect risk factors for the malaria outbreak. Selected case patients and controls were interviewed about the presence of mosquito breeding sites in their compound and near to home within 500 meters or less than it. These sites include unprotected surface water, open deep well, solid and liquid waste collection, and disposal facilities. In addition, the availability of uncovered plastic water containers, old tires, and broken glasses in the home or outside the home was also critically assessed. Similarly, observation of these potential mosquito breeding sites and the presence of Anopheles larvae in stagnant water was conducted. Quantitative data that was addressed socio-demographic characteristics and potential exposures were collected. Laboratory technicians had conducted thick and thin smears with a 100 × oil immersion microscopy at Biftu Health Center of Siraro District. Additionally, Diagnostic Test (RDT) was also used in this health center whenever they faced a shortage of some reagents and during interruption electric power. Health extension workers also used Rapid Diagnostic Test (RDT) to identify confirmed malaria cases at the health post and community level during the outbreak investigation.
A five-year (2017 to 2021), fiscal budget years recorded malaria data at the Siraro health office were reviewed. Daily data to weekly total cases in the affected localities in the previous weeks and months were compiled. By taking the second-largest malaria trend from the five-year reviewed malaria data as a threshold and comparing it with the number of cases of the weeks and months of 2021, the malaria out-break was determined. Data Quality Assurance
We used a line list for describing malaria cases in terms of time, place, and person. However, all data completeness was checked before analysis.
Data processing and analyzing
Data enter and summarizing were done using Epi- Info version 7.2.4.0 software. Then data were imported to Microsoft Excel and analyzed by SPSS version 25. We identified independent determinants by bivariate & multivariate logistic regression.Used a P-Value (< .05) and AOR with 95% CI to report significance and strength of association, respectively.
Ethical considerations
The supportive letter was written by St. Paul’s Hospital Millennium Medical College to Oromia Regional Health Bureau to get permission from the West Arsi Zonal Health department and Siraro district health office.
Dissemination of results
The study finding was prepared to share with St. Paul’s Hospital Millennium Medical College, School of public health of Field Epidemiology Training program Coordinators and mentors, Oromia Regional Health Bureau, and Siraro District Health Office in both hard copy and electronic soft copy.