Defusing panic over Ebola by understanding R-nought

Earlier today it was announced that Thomas Eric Duncan died in Dallas. Duncan, a Liberian national who contracted Ebola in Liberia, did not show symptoms on his journey to Dallas or immediately after his arrival. Various news outlets are reporting that travelers arriving in the United States from West Africa would have their temperatures taken and be asked to answer questionnaires ascertaining any possible exposure.

Given today’s events, it’s understandable that Internet speculation and media coverage have fanned the flames of public panic regarding Ebola. But reporters should be asking state and local epidemiologists if that panic is really justified.

Math can answer that question.

Epidemiologists have calculated a reproduction number, or R0 (pronounced R-nought) to estimate the number of individuals who contract a disease from an infected and contagious individual.

In spite of the epidemic in West Africa that has infected and killed thousands, Ebola has a relatively low R0 – it sits between 1.5 and 2. In comparison, measles (one of the most contagious diseases in the world) has an Rof 18, meaning an infectious individual will pass the disease on to 18 other people if they are not vaccinated. HIV’s Ris 4.

Ris a complex variable dependent on how long disease sufferers are contagious and how much of the virus is needed to infect someone, among other things, but these data indicate that Ebola is, in fact, controllable with appropriate and timely responses from the public health sector.

Ebola, which is transmitted only by contact with infected bodily fluids, is not contagious until the patient begins to show symptoms. Once contagious, concern is warranted, because Ebola fatality rates approach 50 percent, especially without proper treatment.

However, reporters tapping into public health experts who can explain the concept of R0 ,should be able to show how containable the disease is and put it into proper perspective.

3 thoughts on “Defusing panic over Ebola by understanding R-nought

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