NAIROBI, Kenya – The World Health Organisation (WHO) says a country can declare an Ebola outbreak over after completing 42 consecutive days without a confirmed or probable case, provided the countdown begins after the last potential exposure linked to the final case.
The criteria have come into focus as Kenya’s reported Ebola cases rose to seven, prompting health authorities to intensify contact tracing, quarantine and disease surveillance.
WHO says ending an outbreak requires more than treating infected patients and monitoring their contacts. Authorities must establish that human-to-human transmission has been interrupted and that no ongoing transmission chains have been missed.
“The acute phase of the outbreak is defined by the propagation of the virus within communities through transmission of the virus from one person to another,” WHO said.
The organisation states that this phase is considered interrupted when no confirmed or probable Ebola virus disease cases are detected for 42 days following the last potential exposure associated with the final case.
The period represents twice Ebola’s maximum incubation period and is intended to provide additional assurance that transmission has stopped.
When Does The 42-Day Countdown Begin?
The start of the countdown depends on the circumstances surrounding the final patient.
For patients who recover, the countdown follows confirmation of recovery through two negative polymerase chain reaction (PCR) blood tests taken at least 48 hours apart.
When a patient dies, the countdown begins after a safe burial, in line with WHO guidance.
During the observation period, health authorities are expected to maintain active surveillance, search for suspected cases, monitor contacts and ensure rapid-response teams are ready to investigate new alerts.
Testing suspected Ebola-related deaths in communities and maintaining infection prevention and control measures are also essential.
The 42-day period is therefore not simply a waiting period. It depends on continued surveillance and the ability to detect and investigate possible infections.
Why Ebola Surveillance Continues After An Outbreak Ends
Even after an outbreak is declared over, WHO recommends continued surveillance for at least six months.
This includes investigating and testing people who die under suspicious circumstances in the community, maintaining infection prevention measures and keeping emergency response plans operational.
WHO also recommends continued medical care and testing for Ebola survivors for at least 18 months after the last confirmed patient recovers.
These precautions reflect the possibility that infections may have gone undetected and that the virus can persist in certain body fluids of some survivors after recovery.
Contaminated medical equipment can also pose a risk if infection prevention procedures are not followed, while new infections can arise through animal-to-human transmission in areas where Ebola viruses circulate.
For this reason, public health authorities are advised to communicate the end of an outbreak carefully rather than suggesting that a country is permanently free of all risk.
Uganda Offers Recent Example Of The Process
Uganda provides a recent example of how the declaration process works.
Authorities announced the end of the country’s Bundibugyo virus outbreak on August 27 after completing the required 42-day period without a new confirmed case following the discharge of the last patient on July 16.
The process illustrates the importance of establishing that transmission has stopped before formally declaring an outbreak over.
Kenya Steps Up Contact Tracing After Seven Cases
In Kenya, the Ministry of Health confirmed a third case on October 16 involving a 65-year-old woman who was a close relative and primary contact of the first two patients.
The woman had been quarantined since October 6 before developing symptoms and testing positive.
A day later, four additional cases were confirmed, bringing the reported total to seven.
The ministry said 127 of 130 identified contacts had been traced and quarantined, with efforts continuing to locate the remaining three.
Authorities also said the risk to the general public remained low because there was no evidence of community transmission.
The focus remains on identifying and monitoring contacts, detecting any additional cases quickly, and preventing further spread.
Under WHO guidance, Kenya would need to interrupt transmission and complete the required 42-day period from the last relevant exposure before declaring the outbreak over. Continued surveillance would remain necessary even after that declaration.
