Swedish statistician and global health professor Hans Rosling spent three months working as an epidemiologist in the Liberian Health Ministry helping to tackle the Ebola crisis. Here he describes how a firefighting exercise became a detective job once the rapid spread of the disease had been contained.
When thinking about Ebola, many think the whole of Africa, but it is only a very small part of the continent that has suffered from a catastrophic outbreak, mainly Liberia, Sierra Leone and Guinea.
It all began at the end of 2013 in a southern and very remote part of Guinea and then spread across the borders to Sierra Leone and Liberia.
Shorter outbreaks in Senegal, Mali and Nigeria were swiftly brought under control.
Liberia was first infected by Ebola a year ago, in March. The number of newly infected cases per day slowly slowly increased to about five per day in July. This is when it should have been contained, but that opportunity was unfortunately lost, because the virus slipped into the slums of the capital, Monrovia.
There the disease started to spread faster and faster, because each infected person infected, on average, two more.
This caused a doubling in less than a month - this is what statisticians call exponential growth. No country, no society can function for very long with such a rapid increase of such a cruel and terrible disease.
At the end of September 2014 Chris Dye and his team at World Health Organization (WHO) published a landmark study showing that if nothing was done to curb the epidemic curve, the number of cases would skyrocket, continuing to double in less than a month. It was terrifying, as it had gone beyond a humanitarian crisis - it had become an economic and security crisis.
But action was taken and by the end of October the data indicated that the rising curve had been broken and that the number of new cases per day had started to decline.
This is when I joined the epidemiological surveillance team in Liberia.
I had to join the response to this terrifying outbreak as I had research experience of many similar outbreaks in remote parts of Africa.
I went there as a university professor, walked into the Ministry of Health and met Luke Bawo, the head of epidemiological surveillance. He asked me to join him as deputy head of epidemiological surveillance and we shared an office for the 12 weeks I worked in the ministry. My mentor and teacher was Margaret Lamunu, who had stopped Ebola in Uganda a decade ago, and now works for the WHO.
Margaret taught me the specifics of Ebola. And there are a lot of specifics, perhaps foremost the very high contagiousness of the severely sick that makes even data collection difficult.
I became very impressed by the seriousness of purpose and hard work that was put into understanding the epidemic by the leaders and professionals in Liberia. Staff worked past sunset, when the electricity had already been switched off for the night to save diesel. It was highly motivating to work with such dedicated people.
And it was also very inspiring to be part of a very broad international support. It was a new experience for me as a professor from the Swedish Academy of Science to work with the military, such as Gen Gary Volesky, who led the 101 Airborne Division of the US Army and provided crucial transport support, and Maj Morris Hunh from the Chinese People's Liberation Army, who built a big treatment unit in the capital.
Another very positive experience was to report to the president and the most important government ministers - they were very sharp and posed lots of difficult questions. Their seriousness and wisdom impressed me greatly, and the division of tasks was kept clear.
We, the experts in different fields, presented the facts and the policy options, and the politicians listened to us, as well as to the Liberian people, asked questions and made the decisions. I attribute the relatively fast success in the fight against Ebola in Liberia to the strategy adopted by Liberian politicians and professionals.
And this is what happened. The curve turned around because enough Ebola treatment units were built. Medecins Sans Frontieres ran the biggest. When that was not enough, Liberian doctors and nurses added the next treatment unit. But the race against time in September to provide treatment and isolation for all patients, when the epidemic curve climbed to 30, 40 and 50 patients per day, was won by the WHO. By the end of September, Dr Atai from Uganda opened the so-called Island Clinic which meant beds could be offered to all Ebola patients.
The curve was curbed for four reasons:
- The construction of these treatment and isolation units for the sick
- The provision of safe burial, by the Red Cross and other organisations
- Information and mobilisation of communities - posters were one of many ways to swiftly increase knowledge
- A more and more effective system to identify and follow all contacts
The number of new cases per day dropped fast down to about 10 per day. Some thought it would be over by Christmas, but that was wishful thinking. Ebola ends as it started: slowly.
The curve fell fast from 50 cases per day in October to 10 per day by the end of November, after which the fall was slower. By end of the year there were still about five new cases per day, on average.
By then the most important thing was to plan for reaching zero cases. And for this, contact tracking and monitoring became the number one priority. During the catastrophe the response was like a fire brigade fighting a wild fire, but by end of December, with so few cases per day, the response turned into detective work.
We had to reach zero by identifying each and every person that had been in contact with each case, and visit them daily for 21 days. The only thing that makes Ebola easy to fight is that patients are not contagious during the first day of illness. So if they are isolated during the first day the epidemic will end.
In one case, a single infected person passed on the infection to more than 20 people, most of whom died.
So the curve turned downwards and until recently it looked as if Liberia would be declared free from Ebola in April. But that all changed on Friday 20 March when a woman in Monrovia was found to be infected.
Ebola will end as it started: slowly, slowly. And although it was sad that a new case appeared in Liberia, intensive work is under way to get things under control. In this end phase, the national experts and the qualified teams from the African Union are playing a crucial role.
While Liberia has only had one person infected during the last 21 days there are many more in Sierra Leone and Guinea. These two countries are today several months behind Liberia, but the number of cases per day has dropped. However they are fighting with endurance and wisdom.
Dr Tolbert Nyenswah has both endurance and wisdom. As deputy minister of health he leads the Ebola response in Liberia. I am convinced he will lead Liberia to zero cases.
Understanding Ebola: Listen to Hans Rosling and WHO's Margaret Lamunu on BBC World Service.
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