Ebola update

Ebola_2014 graph

Sometimes, with a long drawn out event, we get news fatigue and stop paying attention, even though the calamity is getting worse and worse. So it seems with Ebola.

The fact remains that Ebola is the biggest threat to human life since the 1918 Influenza epidemic, which killed 50-100 million people. Ebola is still doubling in number of infections every 20 days exponentially and it is still killing about 70% of those infected. CDC epidemiologists say it will infect 1.4 million people in Liberia and Sierra Leone alone, which means around a million dead. Cases are popping up around the world now and much vaunted Western public health systems are failing when tested. Politicians and the mainstream media have significantly understated the proven science.

Let’s look at the basic statistics of contagion. If each contagious person infects more than one additional person the epidemic will increase. If each infected person infects less than one additional person the epidemic will fade away. This number is known as the basic reproduction number and is called R0 by science. Measles has an R0 in the range of 12 to 18, which explains how massively contagious it is. HIV has a R0 of 2 to 5, which explains its spread. The 1918 Flu had a R0 of 2 to 3. For Ebola currently the R0 is 1.5 to 2.2.

In the West we have sophisticated public health systems that should keep the R0 below one. In Africa they are trying to reduce R0 by educating people on how to prevent contagion and by throwing foreign medical resources from USA, UK, Cuba etc at the problem. This is where we have failed most. We could have brought R0 down far sooner. We have the resources, we just lacked the political will. We still do. In all 20 previous major outbreaks of Ebola the R0 was brought below one by quarantine, by letting nobody in or out of the village or town till the disease had run its course. Unfortunately with the current epidemic we are far too late for that.

The press have been touting the good news about Ebola being beaten in Nigeria and Senegal, but lets look at the reality. In Nigeria it was one infected man, Patrick Sawyer, who flew there from Liberia. He managed to infect 20 people, 8 of whom died, before public health measures stopped the spread. Senegal closed its border with Guinea way back in March, a very wise move, but one student got through, who subsequently recovered. So these are not massive success stories, they are just a case of disaster averted.

Talking about public health it is worth looking at the GDP per capita of some of these countries. (CIA World Factbook 2013). Liberia $400, Guinea $600, Sierra Leone $800, Senegal $1,200, Nigeria $1,700,(USA $52,800. UK $39,600). So you can see the paucity of their ability to control the outbreak by education and public health measures.

The very good news is that, in the laboratory, we know the Ebola virus extremely well indeed, we have been studying it since 1976. We are very familiar with the clever mechanics it uses to disable the human immune system till a cytokine storm is triggered that kills 70% of those infected. So we can very easily create and manufacture a vaccine. Tens of thousand of doses of this will be ready by the end of the year. By when CDC think that a million people will be dead in just two countries. And the populations of the infected countries are Liberia 4.3 million, Guinea 11.7 million and Sierra Leone 6 million. Total 22 million. Immunisation in society only works by bringing R0 below one. It needs to build up herd immunity. So tens of thousands of doses won’t do that, it will only be enough to protect key health workers. We need millions of doses and whilst we are making them Ebola will continue its exponential spread.

This week we had some very compelling evidence that our governments have been understating the problem. CDC were forced to announce a very big change in the protocol that medical workers should follow to prevent infecting themselves. This was a tacit admission that the dangers of contagion of the virus were much greater than they had been saying before. Something that was already evident from laboratory research.

So Ebola is now a public health and statistical problem. A matter of applying a number of mechanics to get R0 below one. It is widely thought that Western public health systems are robust enough to maintain this. So there are two elephants in the room. The first is what happens if (or when) Ebola reaches China, India or even Indonesia. Do they have the public health resources to contain it? The second is virus mutation. Right now several tens of thousands of  people are carrying the virus. In their bodies it is multiplying many of millions of times an hour. So very many mutations are happening, just as they happen with Flu viruses. The big dangers are that the disease increases in contagion and that it evolves to beat the vaccine. So we still need to be very worried.

So there you have it. Still don’t relax and still don’t fly.

 

 

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