Discussion

A single, traditional funeral likely led to a sharp increase in Ebola cases in a previously low-incidence district in Sierra Leone, suggesting a substantially higher rate of secondary transmission from one patient than the basic Ebola virus reproduction number of 2.53 estimated for the outbreak in Sierra Leone (4). A high number of secondary cases might be explained by a high viral load in the primary patient, the type of contact, timing of contact (e.g., while a patient was alive or dead), the number of persons exposed, or a combination of these factors. An investigation of the 1995 Ebola outbreak in Kikwit, Democratic Republic of the Congo, identified 38 secondary cases linked to one patient who had many visitors while hospitalized (5).

Eight men with confirmed Ebola who attended this funeral died. The high case fatality rate among men might be explained by more intense or prolonged contact with the corpse by the male funeral attendees. According to traditional funeral practices in Sierra Leone, family and friends of the same sex are often responsible for preparing, washing, and clothing the body (6). Funerals pose a substantial risk for Ebola transmission for several reasons. First, the risk for transmission might increase with viral load, which is often highest in nonsurvivors, especially during the later stages of disease progression and at death (7). Second, the traditional practices of washing, preparing, and touching the body include direct, prolonged contact with the corpse. Finally, funerals attract family, friends, and colleagues from various locations. Attendance is important to demonstrate respect, establish land rights, and determine whether widows will return to their community of origin (6). Travelers who are exposed and become infected can establish new chains of transmission when they return to their original communities.

This report highlights the potential for high levels of transmission from a single patient or event and underscores the importance of vigilant Ebola surveillance and response. At least 36 Ebola cases and nine deaths might have been prevented had the pharmacist had a safe, medical burial. The DHMT’s comprehensive and targeted response, including rapid community engagement, quarantine, and active surveillance through daily house-to-house visits and formation of a youth neighborhood watch, likely led to the prompt identification of cases and limited transmission beyond the four cases in the second generation and the four cases in the third generation.

Fear, stigma, and discrimination might lead to underreporting of Ebola cases (8), and there was likely underascertainment of Ebola cases, deaths, and exposures. During the time of the investigation, Moyamba DHMT and CDC witnessed and received anecdotal reports of persons who were fleeing the area and hiding from surveillance and contact tracing teams. Self-reported data are limited by patients’ and proxies’ ability to recall exposures and dates, and social desirability bias and fear might have led to underreporting of Ebola symptoms and contact with ill persons or corpses.

To achieve and maintain zero new infections, enhanced community-based surveillance strategies, such as the community event-based surveillance system, which employs community health monitors to detect and report Ebola trigger events (e.g., two or more ill or dead family or household members) (9), are critical to the rapid identification of high-risk events to prevent transmission. Safe, dignified burials by trained burial teams using appropriate protective equipment are critical to the interruption of transmission and control of Ebola in both low-incidence and high-incidence settings, as well as in rural and urban settings (10). Early identification of Ebola cases along with prompt isolation, testing, and care of patients can limit transmission, improve likelihood of survival, and ensure safe burials of persons who die, ultimately preventing deaths from occurring at home and unsafe burials in the community. Ebola response teams can strengthen community Ebola surveillance.