On 31st August 2018, a community member, reported the of death of his niece. The niece, a child from Daro Dima village, had a history of paroxysmal cough, post-tussive vomiting and respiratory whoops for 19 days. In addition, the community members were informed of the death of three more children with similar illness in August 2018 in the same neighborhoods as well as similar health problems affecting almost all children in the village.
On September 1st, 2018, Dara Malo district Health Office revitalized the rapid response multi-sectoral committee and reviewed its Risk and Emergency Management Plan. The district health office allocated 1850.00 USD and purchased drugs and supplies. On the same date, the district health office request technical, and other resources support from Gamo Zone Health Departments, SNNP regional health bureau, Ethiopian Public Health Institute (EPHI), World Health Organization, USAID’s Transform: PHC project and other development partners.
The PHEM core process established and deployed epidemic investigation team which comprised a field epidemiologist, an integrated diseases surveillance response officer and health extension workers. The team members were oriented on the case definitions, diagnosis and treatment protocols, strengthening community-based surveillance, and enhancing community mobilization strategies.
Verifying the pertussis outbreak
The index case , a five-year-old child with unknown vaccination status was identified from Daro Dime village on 1st September 2018. The reported pertussis suspected case presented at Daro Dime Health Center with a complaint of paroxysmal cough, post-tussive vomiting and respiratory whoop since 2nd August 2018. The source of infection for the index cases was not documented. The case was treated with trimethoprim-sulfamethoxazole (TMP- SMZ) with a dose of trimethoprim 8 mg/kg/day, sulfamethoxazole 40 mg/kg/day in two divided doses for 14 days. The outbreak investigation team regards this probable case as the index case of the current pertussis outbreak. The case had a cough of more than two weeks, with inspiratory whoop and post-tussive vomiting. The district health office and Daro Dime Health Center instituted active case search from 4th to 13th September 2018. Over the period, 471 suspected and probable pertussis cases were identified in five kebeles. The outbreak investigation team-oriented community leaders, health workers and elders. Active case search was extended through 27th March 2019. Over the whole surveillance period a total of 1840 suspected, probable and confirmed pertussis cases including six deaths, were identified.
Descriptive analysis of Reported Pertussis Outbreak
The pertussis outbreak line-list is described in terms of time, place and person.
Demographic distribution of the cases
From 1st September 2018 to 9th January 2019, there were a total of 1840 reported cases of pertussis. Of the reported cases 9 (0.5%) were confirmed (all due to Bordetella pertussis) while 454 (24.7%) were probable cases and the rest 1377( 74.8%) suspected cases. The socio-demographic characteristics of the study participants are shown in Table I. Dara Dime village reported 838 (45.5%) of the pertussis cases. The age of the cases ranged from 1 month to 50 years of age with a median of 36 months. Of the total cases, 230 (12.5%) were aged less than six months while 801 (42.5%) were 1 to 4 years old Table 1.
The overall attack rate was 1,708/100,000. The attack rates by age category were 12,689/100,000, 5,965/100,000 and 667/100,000 reported in under one-year infants, 1 to 4 years children and 5 or more years of children and adults, respectively (additional file 1).
A total of six deaths due to pertussis were reported to give a total case fatality rate of 3.3 deaths per 1000 cases. These include five deaths from Daro Dime and one death from Menena Aba kebele. Two deaths each were under 6 months, and between 6 to 12 months. One death each were from 1 to 4 years and 5 to 9 years. The highest case fatality rate was found among infants less than 5 months of age with a case fatality rate of 8.7/1000 cases, followed by infants aged 6 to 11 months with 4.85/1000 cases (Figure 1).
The most frequent presentation was paroxysmal cough which was a complaint in all 1840 (100.0%) cases. This was followed by post-tussive vomiting which was reported in 1579 (85.8%). Inspiratory whoop was reported in 454 (24.7%) while 136 (7.4%) had low grade fever. In addition, 37(2.0%) of the cases had additional signs and symptoms indicative of severe illness. The most frequently reported signs of severity were syncope and apnea in eight (21.6%) and six (16.2%) cases, respectively Figure 2.
Descriptive Analysis by Time
Figure 3 below presents the Epi-Curve which plots the frequency of pertussis cases over time by date of onset of paroxysmal cough and date cases identified by health workers, respectively. The epi-curve presented below clearly demonstrate the classic propagated or progressive source nature of pertussis outbreak, where three peaks observed over time. The mean delay to seek medical care by patients or care takers were 9.4 days, with median of 7 days ranged from one day up to 63 days.
Geographical distribution of the outbreak cases
The highest attack rate was reported from Dara Dime village while the highest case fatality rate was noted in Menena Aba village. Figure 4 depicts ArcView GIS spatial analysis pertussis case attack rates and case fatality rates by village.
The vaccination status of pertussis cases was collected from reviewed EPI registers at health posts and oral report of family members or care takers. Number of cases who had received a pertussis-containing vaccine was found to be 169 (9.2%), 321 (17.4%), and 761 (41.4%) for one dose, two doses and three doses, respectively. Of the rest of reported pertussis cases 232 (12.6%) had not received any vaccine dose while 357 (19.4%) had unknown immunization status.
Management of the pertussis outbreak
There were delays in notification and lack of timely proper management of probable or suspected pertussis cases in the community. The health workers were treating cases as pneumonia, pertussis was never suspected until the death of four children occurred due to the outbreak.
The outbreak response team lobbied community leaders and elders to mobilize the community to report cough of 2 weeks or more to nearby health posts. Information leaflets were developed and distributed to all household members using local language, Gamo.
Individual cases were treated with antibiotics to reduce severity and duration of symptoms, and to prevent complications. From 1st September to 22nd December 2018, 1832 (99.5%) of the identified pertussis cases were treated with amoxicillin, cotrimoxazole or erythromycin. The outbreak response was hindered by lack of sufficient erythromycin syrup doses for children under five years of age.
In order to reduce the spread of infection, a Mass Drug Administration (MAD) program was initiated following a facilitated two days training for 110 health workers including 90 drug distributors, 17 supervisors and three district coordinators. The MDA was conducted from 23- 27 December 2018 using Azithromycin with a dose of 10 mg/kg/24hr, P.O. once under direct supervision of health workers on first day followed by 5mg/kg/24hr, P.O. from 2nd to 5th day. This prophylactic mass campaign targeted 69,587 residents of the 14 pertussis-affected villages. Directly observed azithromycin therapy was received by 67236 (96.6%) people under supervision of health care providers. Among these, 21,003 (31.2%) were under 10 years of age. The campaign required $18325.00 USD of investment from the district health office and partners for its successful implementation.
Prevention of spread of infection
EPI register reviews and oral responses of patients or care takers were counted and mapped for supplementary immunization campaign. After completing prophylactic antibiotic treatment with azithromycin, the outbreak management team organized pentavalent vaccination campaign from 24th – 28th January 2019. A total of 665 children were vaccinated including 266 who received their first dose, 180 second dose and 219 the third dose of pertussis containing vaccine.
All schools were closed for the period of mass preventive prophylaxis campaign while community members were advised to avoid participating in local markets. In addition, community members were advised to implement strict personal hygiene including frequent hand washing and avoiding contact with pertussis suspected individual.
Following the last reported case, the District Health Office continued active case search for more than two months on daily bases. The outreach investigation team continued to provide support for individual case management, mass health education for community members and enhance the capacity of health workers on cold chain management, defaulter tracing, and use of data for decision making. After no further cases of pertussis were reported from 10th January to 27th March 2019, the investigation team was demobilized.
Formulate the hypothesis
The outbreak investigation team reviewed the surveillance reports filled by four health centers and fourteen health posts and six private health facilities and organized by Dara Malo district Health Office. Based on the routine surveillance report, the completeness rate was assessed as high with a completeness rate of 84.0% in 2016/17; 88.0% in 2017/2018; and 91.0% in 2018/2019. In addition, housing conditions, vaccine potency and vaccination coverage status of affected community were identified as a major factor contributing for the pertussis outbreak occurrence.
The housing condition and family size per household was assessed. The average house in affected community had 7 people and lacked air circulation. Community members were encouraged to open ventilate their homes.
Cold chain, immunization services management
Wacha Health Center has high tension electric power supply. Three out of four health center have solar panel to get un-interrupted electric power for cold chain maintenance. All fourteen health posts were collecting vaccine on scheduled vaccination campaign and outreach services. The investigation team did not find continuously recorded temperature monitoring tools. And the observed vaccine vial monitor (VVM) which is a thermochromic label on vials, revealed that the vaccines were kept at temperatures which do not preserve vaccine potency. Overall cold chain maintenance was generally found to be poor.