Why Scientists Say Ebola Will Surge But Then Level Off Before The Disease Takes Over The World

[cali]

With scientists projecting that the West African Ebola epidemic will mushroom, many people are asking how experts can be so sure it will hit a peak and come back down, considering there’s no vaccine or reliable treatment yet. Right now, the trend is steep and upwards. Of the more than 8,000 cases so far, most infections occurred in the last 3 to 4 weeks, said David Peters, Chair of the Department of International Health at Johns Hopkins University, where he and other experts gathered for a meeting Tuesday. The World Health Organization has projected a possible 10,000 new Ebola cases per week in West Africa by the end of this year.

How do they know when this frightening upward curve will level off, or if it will level off at all, as opposed to spreading around the globe and ravaging the human race like the pandemic in the movie Outbreak? The most dire forecast comes from the Centers for Disease Control and Prevention, which predicted 1.4 million cases by early 2015. But even their graph levels off and then falls as the number of new cases eventually go to zero.

To understand what goes into these forecasts, I talked to Joshua Epstein, a professor of emergency medicine at Johns Hopkins and an expert on disease modeling. He spoke Tuesday at a meeting, Dean’s Symposium on Ebola: Crisis, Context and Response, held at the University’s Bloomberg School of Public Health. In his talk and in a discussion afterwards, he explained not only why the virus is unlikely to destroy the human race, but why he thinks it’s unlikely to reach the CDC’s prediction of 1.4 million cases. On the more pessimistic side, however, he said he’s not sure this outbreak will ever be completely extinguished. In his projection, the number of new cases hits a peak, then falls, but not to zero.

Even without a vaccine, he said, the current outbreak will eventually “run out of fuel” as infected people either die or become immune. So far, at least, it appears that people who survive the disease aren’t vulnerable to reinfection. Right now the virus is spreading through areas with lots of vulnerable people, he said. In the countries that are most affected – Sierra Leone, Guinea and Liberia – people are getting infected through funeral customs that involve washing the dead. And sick people are infecting others, since those countries lack adequate facilities to isolate patients. That was a refrain at the meeting – in the affected countries there aren’t nearly enough health workers, hospital beds or ambulances to safely transport them to hospitals.

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In Africa, there are some big variables that make it hard to predict how far this outbreak will go, however. Epidemiologist Michael Osterholm of the University of Minnesota said one of those variables is the fact that in the fall after harvesting season is over in West Africa, young men migrate into Central Africa to work in gold mines, illegal charcoal operations or cocoa plantations. To describe his concern, he uses a fire analogy. “If West Africa was a can of gas waiting for a match, the rest of Central Africa is a tanker truck of gas,” he said in an invited talk during Tuesday’s meeting.

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http://www.forbes.com/sites/fayeflam/2014/10/15/why-scientists-say-ebola-cases-will-keep-rising-but-disease-will-not-take-over-the-world/

[cali]

1. kick

[HereSince1628]

2. Perhaps, true, but that's not especially reassuring...

Equilibrium prevalence can be worked out of 100 year old mathematical models of epidemics, as a balance of rates of transmission and recovery (or death).

But, the same is true of wild fire which is conceptually something people can better understand.

If you think about pictures and video you've seen of grass, brush, or forest fires, you'll recognize that what's burning is usually pretty small relative to the zone of destruction the wildfire leaves behind as it spreads. That's the balance between whats burning and what's burned. What is on fire is just the boundary of the area burnt, a relatively thin fireline (the equilibrium prevalence) moving away from a zone of charred landscape that is often many times greater often a couple orders of magnitude greater.

We shouldn't be reassured. There's going to be a staggering amount of death with the current ebola epidemic.

The deaths will bias toward people who provide care, from mothers, sisters and aunts to Drs and nurses. Areas are going to run out of care-givers. Suffering from -all- causes is going to multiply.

Misery is going to happen at epic levels. A moral, empathetic world would be rushing to mobilize resources that are going to be needed to put out the fire, and to deal with the aftermath.

[magical thyme]

3. agreed. I think a wildfire is an excellent analogy

not to mention a wildfire that occasionally gets on buses, trains and planes and starts small fires in other areas.

And most of those other areas are also 3rd world countries that will be seriously strained to contain new outbreaks.

They never, never, never, never should have let this go as far as they did before starting to respond.