Ebola - Good news, bad news!

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Wednesday, 22 October, 2014

Good news at last in the fight against Ebola: Senegal and Nigeria have controlled their outbreaks and are now declared free of Ebola. The criteria is no new cases of Ebola 42 days after the onset of the last case. The magic figure "42" is equal to 2 maximum incubation periods for the disease. Maximum incubation period for Ebola is 21 days. The other good news is that the reproductive rate of the epidemic in the Democratic Republic of the Congo is now less than 1.

Reproductive rate is the number of new cases arising from each case of a disease. When the reproductive rate of an epidemic is >1, a pathogen spreads and the epidemic grows; when the reproductive rate is less than 1, the epidemic collapses. For example, the West African epidmic has a reproductive rate of about 1.3. Hence, every case of Ebola causes 1.3 new cases (on average).

A brilliant paper by Maganga et al (2014) describes the current epidemic in DRC, a separate outbreak from the one in West Africa. As of 9 October there had been 68 cases with 49 deaths (case fatality rate of 72%). It is a fascinating story that started when a husband presented his wife with a monkey he found dead in the forest. Unfortunately, the monkey had died from Ebola. While preparing the monkey for a meal, she became infected, developed Ebola virus disease (EVD) and died. She was pregnant and because it is a custom to separate a dead baby from the mother in that area prior to burial, a doctor and three nurses did a post-mortem casearian. They all became infected with Ebolavirus and the epidemic spread. In the early stages of the epidemic the reproductive rate was 1.29 - hence it grew. Now after effective intervention by the DRC health department and MSF, the reproductive rate is 0.84 (i.e., <1.0) and the epidemic is collapsing. The index case was a superspreader, causing 21 secondary cases. Read the full story here.

Bad news is that the Ebola epidemic in Guinea, Serria Leone and Liberia continues to grow. Although there are many doctors, nurses and others globally willing to assist in West Africa, the bottle neck for foreign medical teams is that there are not enough organisations willing to run Ebola treatment centres (ETC). It is too dangerous for individual health care workers to operate alone; team support is needed. However, governments, NGOs and other organisations to take responsibility for an ETC are not stepping forward. By the end of October, 20 ETCs will lack medical teams. Tragic!

Literature cited
Magana et al. Ebolavirus disease in the Democratice Republic of the Congo. New England Journal of Medicine 2014;Oct 15. [Epub ahead of print]
Posted by Rick Speare