As Kenya grapples with an Ebola outbreak, citizens are beginning to ask when the country can officially declare the outbreak over.
The answer is not as simple as treating everyone who has contracted the virus or reaching a point where no new cases are being reported. According to the World Health Organization (WHO), a country must go through a carefully defined monitoring period to establish that human to human transmission has been interrupted.
At the centre of this process is the 42 day rule, an internationally established benchmark used to determine when an Ebola outbreak can be declared over. The period is equivalent to twice the maximum incubation period for Ebola, which is 21 days. In other words, health authorities must establish that no new confirmed or probable cases have been detected for 42 consecutive days after the last potential exposure associated with the final case.
The rule is intended to give health officials sufficient time to identify infections that may not have been detected earlier and establish whether any transmission chains remain active in the community.
Kenya’s outbreak has made the question particularly relevant. By October 18, 2026, the country had recorded eight confirmed Ebola cases, according to reports citing the Ministry of Health. The outbreak began with a man who had travelled from the Democratic Republic of Congo and died in a Nairobi hospital on October 5. Subsequent infections included people who had been in contact with him, among them family members and health workers.
The emergence of additional cases shows why authorities cannot simply begin counting down to the end of an outbreak as soon as the first patient dies or is discharged from hospital. Each newly confirmed infection requires health teams to investigate possible exposures, identify contacts and establish whether further transmission has occurred.
So, when does the 42-day countdown actually begin?
According to WHO guidance, the starting point depends on the circumstances surrounding the last confirmed or probable case. If a patient recovers, the countdown begins on the day after a second negative polymerase chain reaction (PCR) blood test, provided the two tests were collected at least 48 hours apart. If the patient dies in an Ebola treatment centre and a safe burial is conducted, the countdown begins the following day. Similar provisions apply when a suspected or probable Ebola death occurs in the community and the person is buried.
This distinction matters because the countdown is not simply a period of 42 days after the last patient is admitted to hospital, nor does it necessarily begin when the last patient is discharged. Authorities must account for the possibility of exposure and ensure that the final case has been managed according to the required protocols.
The monitoring period also depends on health officials being able to identify and investigate suspected cases. During these 42 days, authorities are expected to maintain active surveillance, trace and monitor contacts, investigate alerts and ensure that health facilities can rapidly detect and respond to suspected infections. Suspected Ebola-related deaths in the community may also require testing.
If another confirmed or probable case emerges, health officials must investigate the circumstances and reassess whether transmission has truly been interrupted. The appearance of a new case could indicate that an existing chain of transmission was missed or that a new infection has occurred.
The process is therefore about more than the passage of time. It requires evidence that the virus is no longer spreading from person to person through the outbreak under investigation.
There is also an important distinction between ending an outbreak and eliminating every possible future risk of Ebola infection. WHO recommends that surveillance and response activities continue for at least six months after an outbreak is declared over. This includes maintaining systems for detecting suspected cases, testing unexplained deaths where appropriate and ensuring that rapid response teams remain ready to act.
Survivors also require continued attention. WHO recommends ongoing medical care and testing for Ebola survivors for at least 18 months after the last confirmed patient recovers. This is part of a broader effort to manage the possibility of renewed transmission and ensure that survivors receive appropriate support.
The risk of a new case does not automatically disappear when the 42-day period ends. Ebola can re-emerge through a new introduction of the virus, a previously undetected transmission chain or other routes associated with the virus’s persistence. This is why public health authorities are encouraged to communicate the end of an outbreak carefully rather than suggest that a country can never experience Ebola again.
Uganda provides a recent regional example of how the process works. On August 27, 2026, WHO and the Africa Centres for Disease Control and Prevention announced the end of Uganda’s Bundibugyo Ebola outbreak after 42 consecutive days without a new confirmed case following the discharge of the last patient on July 16. The announcement followed sustained surveillance and response efforts, demonstrating the importance of maintaining monitoring systems even after the last patient has recovered.
For Kenya, the immediate priority remains containing the current outbreak, identifying every contact and preventing further transmission. The 42-day period cannot be meaningfully counted towards an end-of-outbreak declaration until the relevant criteria have been met.
Ultimately, the WHO rule provides a clear benchmark, but reaching it requires more than waiting six weeks. It depends on effective contact tracing, reliable testing, safe management of patients and deaths, and surveillance capable of detecting infections that might otherwise go unnoticed.
