Explainer: Why travellers with Ebola can sometimes move through countries undetected
A woman sanitizes her hands before entering at the Kenya immigration services to access port health services at the Busia One Stop Border Post.
An explainer based on the World Health Organisation infographic “Why a traveller with Ebola can move through 3 countries without being detected”
A person can catch Ebola, have no symptoms, board a flight or a bus, cross borders and arrive in a third country before anyone knows they are infected. This is not a failure of one airport or one government. It comes from how the disease behaves and what routine screening can and cannot do. Here is how it works.
What is the main point?
A person infected with Ebola can look and feel healthy for days. Routine travel screening does not test for Ebola. Put those two facts together and an infected traveller can pass through three countries, or more, without being detected.
What is the incubation period?
It is the time between infection and the first symptoms. For Ebola, it runs from 2 to 21 days. Typically, it is 8 to 10 days before the symptoms could appear.
During this time, the person feels well and appears healthy. Nothing about them signals illness.
Is the person contagious during this time?
No. A person is not considered contagious until symptoms start. That means a traveller in the incubation period is not a risk to the people sitting next to them. But it also means there is nothing visible to catch at a checkpoint.
What do the first symptoms look like?
They are not specific to Ebola. The graphic lists fever, headache, muscle pain, nausea and vomiting, and diarrhoea. These look-like common illnesses including malaria, flu, COVID-19 and a stomach infection.
A traveller with mild symptoms could easily put them down to any of these, and so could a screener.
How does routine travel screening work?
Most airports, land borders and ports do not routinely test for Ebola. Screening usually has three parts:
* A temperature check
* A health declaration form
* A visual assessment for illness
Why can screening miss a case?
Each of the three checks looks for signs of illness. A person with no fever, or only mild symptoms, can pass through. If they are still in the incubation period, they have no signs to find. Their form may say they are well, and honestly so.
Ebola is confirmed by laboratory testing, usually RT-PCR, antigen or antibody tests. Testing is not part of routine travel screening.
When is a test done?
Testing is typically done only when one of three things applies:
* The person has symptoms consistent with Ebola
* There is a known exposure history
* Public health authorities identify a potential risk
If none of these is flagged, no test happens.
How could one traveller cross three countries? Walk me through it.
The graphic gives an illustrative example.
Day 0. The traveller is exposed and infected in Country 1.
Days 1 to 3. The traveller leaves Country 1 by air, bus or land. There are no symptoms. They pass routine screening.
Days 3 to 6. The traveller continues to Country 2, for example by connecting flight or land border. There are still no symptoms, or only mild, non-specific ones.
Days 6 to 10 and beyond. The traveller arrives in Country 3. They are still symptom-free, or have mild symptoms that look like common illnesses. They pass screening again.
Day 2 to 21. Symptoms may begin. They can start at any point in this window, typically 8 to 10 days after infection. The person may then be detected if they seek care.
By the time the illness shows itself, the traveller may be in a different country from where they were infected.
How does Ebola spread?
Ebola spreads mainly through direct contact with the blood or other body fluids of a person who is sick with symptoms. It can also spread through contaminated materials, such as bedding and clothing. The body of someone who has died from Ebola can also spread it.
Does Ebola spread through the air?
No. The graphic states that Ebola does not spread easily through the air. Casual contact with an infected person, without exposure to body fluids, is not considered a risk.
What should I do if I have been exposed to Ebola?
Monitor your health for 21 days. Seek medical advice if you develop symptoms.
What if I feel ill after travelling to an affected area?
If you develop fever or other symptoms after travel to an affected area, call your healthcare provider before travelling to a facility. This lets the facility prepare before you arrive.
What do countries need to do?
The graphic says countries need strong surveillance, contact tracing, laboratory testing and coordinated public health measures to detect and respond to cases.
The point is that screening at the border is one layer, and a thin one. Once a case is detected, the response depends on finding the people the patient has been in contact with and testing those who are at risk.
What are the key takeaways?
- A person can be infected with Ebola and feel well for 2 to 21 days.
- They are not contagious until symptoms start.
- Early symptoms can resemble malaria, flu, COVID-19 or a stomach infection.
- Routine travel screening does not include Ebola testing, so a traveller can move through three countries, or more, without being detected.
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