Epidemiological link of a major cholera outbreak in Greater Accra region of Ghana, 2014

We carried out a descriptive cross sectional study to investigate the epidemiological link of the 2014 cholera outbreak in the Greater Accra region of Ghana (GAR). The Greater Accra Region has 16 local government administrative districts (Fig. 1). It lies in the South East of the country along the Gulf of Guinea and has miles of beautiful coastline especially in the rural parts of the region. It is the smallest of the 10 Administrative Regions of Ghana in terms of area, occupying 1.4% of the total land area of Ghana. However, the region contains 15.4% of Ghana’s population, making it the second highest populated region after Ashanti region. It has a growth rate of 2.8%, which is above the national average of 2.4% and has the highest population density in the nation. The 2014 Family Health Annual Report of the Ghana Health Service gave the population of Greater Accra Region as 4,530,905 [14]. The main source of drinking water for about 80% of the households in the region is pipe borne. However, the common source is outside the house. About 50% of the households in the region use mainly public toilet facility or water closets in their houses. Over half of the households in the region dispose of solid waste at public dumps.

The study population consisted of all the index cases, both males and females regardless of their demographic characteristics in all districts, municipals and metropolitans that experienced the 2014 cholera outbreak in GAR. Index case was defined as the first documented case of a contagious disease in a group or population that serves to call attention to the presence of the disease.

There was an extensive review of records of the 2014 cholera outbreak in all the districts with cases by the use of the line lists. Affected districts were identified and visited. In the districts, line lists from facilities with cases were reviewed to identify their index cases, this was done with the help of the District Disease Control Officer. Identifying characteristics of the index cases were; the date of onset, date seen at health facility, name, client’s folder number and address. The folder number was then used to trace the client’s folder additional information such as contact persons and detailed residential address with telephone numbers. The Index case for each affected district was identified and traced by their details provided into their respective communities in GAR. They were then interviewed in their homes after consent had been obtained.

Data for this study was obtained from both primary and secondary sources. Primary data included information from interview of index cases, environmental assessment and GPS coordinates. Secondary data was extracted from records obtained by reviewing existing line lists and client folders at the various levels from the various facilities.

An extensive review of all district records on cholera cases in the GAR was carried out. Index cases were identified with the help of line lists and cases’ folders used to obtain additional relevant information to trace index cases. A questionnaire was administered to all index cases in the affected districts to identify the possible modes by which they contracted the disease as well as their link to any of the cases from the other districts.

The linkage was drawn based on the history of visit, people contacted, as well as food and water consumed prior to the onset of the disease. An environmental assessment of the permanent residence of each index case was carried out and a digital camera was used to capture a photograph of the environment. The GPS co-ordinates of each residence was also taken by standing in front of the house.

Data was cleaned, checked for consistency and analyzed using STATA version 13 and Arc GIS version 10. We performed descriptive analysis of the outbreak data by person, place and time. Univariate analyses were expressed as frequency distributions, percentages, mean ± SD, and rates (attack rates, case-fatality rates etc.) as appropriate.

Maps were drawn using Arc GIS to describe the pattern of transmission and show the areas where index cases live and the distribution of all cases by district. Different geographic areas (districts and communities) were shaded in different colours for easy identification and comparisons. Epidemic curves were also drawn to show patterns of 2014 cholera outbreak distribution for the region and the respective districts. Linkage was drawn based on the history of visit, people contacted and food and water consumed. Pictures of the environment of index cases taken were also presented as environmental analysis.

Ethical approval was granted by the Ethical Review Committee of the Ghana Health Service. Formal permission was obtained from the Greater Accra regional disease control unit as well as at the district health administrations. In addition, the objectives of the study were explained to the participants (index cases) and their consent obtained through a written informed consent document before soliciting information on a scheduled date. Subject codes were used to ensure respondents’ identity remained anonymous and ensure confidentiality.

Table 1 shows the demographic characteristics of cases recorded in the 2014 cholera outbreak in the Greater Accra Region. Up to 20,199 cholera cases were recorded. Children under 5 years of age recorded the least number of cases (2.8%). The mean age of the cholera cases was (29 ± 6.9) years. Sixty percent of the cases were between 20 and 40 years and about 58% (11,694) of the total cases were males.

There was an increase in CFR as age increases. Cases under 5 years recorded the least CFR (0) whilst cases above 40 years recorded the highest CFR (1.4%). CFR was also higher in males (0.7%) than in females (0.4%) (Table 1).

Cholera cases were reported in 15 out of the 16 districts. The Accra Metropolis recorded the highest number of cholera cases (52%, 10,504). The least number of cases were seen in Ningo Prampram district (0.11%, 22). Ashaiman and Ningo Prampram did not record cases below the age of 5. (Table 2).

Ada West district did not report any cases. The districts with high case fatality rates were La Nkwantanang, Ashiaman, Ledzokuku Krowor, Ada East and Tema metro (Refer to Additional file 1). The region recorded an attack rate of 445 per 100,000 population with Case Fatality Rate (CFR) of 0.60% (Table 3). Fig. 2 shows a spot map of cholera cases by districts and shows that a higher burden of cases were found in the Western part of the Region.

The epidemic curve describes the 2014 cholera outbreak as a propagated outbreak. The year started with no confirmed cases recorded for the first 23 weeks in the GAR. The first positive case was confirmed in week 24 (9th June 2014), when the epidemic began. Five more districts confirmed between week 27 (30th June, 2014) and 29 (14th July, 2014). By the 33rd week (11th August, 2014), all districts in the region had reported cholera cases with the exception of Ada West. The epidemic reached its peak during the 35th week (25th August, 2014) and drastically reduced when national interventions to control the outbreak were initiated. It then declined steadily during the 49th week (1st December, 2014). Few cases were still reported till the end of the year but the pace of reporting was slower (Fig. 3).

Epidemic curves for the affected districts can be found in the Additional file 1.

A total of 15 index cases were identified and interviewed from the 15 affected districts. GAR 2014 cholera outbreak started when a 10-year-old girl reported to the Ussher Polyclinic, a facility in the Accra Metropolis. She reported on 10th June, 2014 with onset of the disease from the previous day. Stool specimen from her proved positive to Vibrio cholerae 01 of the Ogawa sub type. The laboratory confirmation came in after she had been discharged. Follow up investigation revealed that the evening prior to the onset of diarrhoea she ate rice and fried turkey tail (locally called Tsofi) from a street food vendor at Agbado, a suburb of Accra Metropolis. Another case was confirmed in Maamobi polyclinic, another facility in the Accra Metropolis within the same week. After the second confirmed case, the Accra Metro began to experience an upsurge in the number of cholera cases reporting. The next affected district after Accra metropolis was Adantan municipal whose first case reported on 1st July 2014. This was a woman who trades at the Makola market, believed to have gotten the infection whiles there and exported the disease to her district. Ashiaman recorded their first case on 4th July 2014. The case was a 24 yrs. old male who came on vacation from school and usually visits his friends who runs an internet café in Accra. He spends most of his with them and eats from there. All the other districts had a contact in the Accra metropolis with the exception of Tema and Kpone Katamanso. Kpone Katamanso district index case can be traced to Tema where a caterer visits Tema on commercial purposes during which there was an ongoing cholera transmission. She gets herself infected and exports the infection to her community, Apolo in Kpone. Tema’s index case was a fisherman who is always on the sea fishing. He started experiencing signs and symptoms of the disease on 19th July 2014 when by then there were existing outbreaks in six districts. Tema is surrounded by four out of the six districts, ie. Adentan, Ashiaman, La Dadekotopon and Ledzokuku Krowor. However, Tema and Accra metro are linked to each other by the sea were fishing activities take place.

Results from the interview reveals that 80% (20) had traveled or visited the Accra metropolitan areas. There were various communities in the Accra Metro where index cases visited, these places included; Darkuman, Dansoman, Chorkor (Ablekuma sub-metro), Lapaz, Achimota (Okaikoi sub-metro), Kwame Nkrumah circle (Osu Clottey sub-metro) and Accra central (Ashiedu Keteke sub-metro). Two-thirds of the index cases ate food prepared outside their home and had visited the Accra Metropolis (Table 4).

Environmental conditions of the communities within which index cases for the various districts lived were assessed. Pictures (Fig. 4) of the environment were taken to be able to well describe it. The various environmental conditions within which index cases were found can be described as unhygienic and unclean. There was generally poor environment sanitation. There was crude dumping in most of the places visited. There was open defecation in some of the places. This was because most of the households did not have a place of convenience attached to them. Inhabitants patronize the public latrines. The cesspit emptier that empties these liquid wastes end up emptying its content into the sea. There were inadequate drainage and sewage systems. Inhabitants resort to dumping at sea and in gutters when it rains. Continuous water supply was another major problem in these areas. They mostly depend on the sachet water as the safest source of drinking water.