Ebola

Yes, measles' R0 is well above 2. Above 10, in fact. It's one of the many viruses that I alluded to that have R0 > 2.

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Which of these is more worrisome:

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1. A disease with a 90% mortality rate that infects 10,000 people.

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2. A disease with a 0.1% mortality rate that infects 1 billion people.

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Depends. Is disease 1 permanently confined to those 10,000, or are freely infecting others?

If that outbreak is confined to 10,000, which is more worrisome?

In case 1 you have 10% survivors or 1,000 survivors with antibodies to pass on to descendants. If they are carriers then potentially 90% of human population could die.In case 2 you have 99.9% survivors or 999 million survivors with antibodies to pass on to descendants. If they are carriers then potentially 0.1% of human population could die.So case 2 is less worrisome from a population survival point of view.Enjoy

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If that outbreak is confined to 10,000, which is more worrisome?

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I wouldn't call either one worrisome. Disease 2 will certainly kill more people. What's the point?

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In case 1 you have 10% survivors or 1,000 survivors with antibodies to pass on to descendants. If they are carriers then potentially 90% of human population could die.

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You don't pass antibodies to your descendants.

More specifically, there is no record (AFAIK) of any virus in vivo evolving mechanisms for airborne transmission.But this possibility is not so remote that we shouldn't give it some consideration.We know that there are evolutionary pathways that can readily make a viral strain airborne. See the laboratory work by Herfst et al., 2012 ("Airborne transmission of influenza A/H5N1 virus between ferrets").Additionally, Ebola (specifically, the ZEBOV strain) has shown evidence of airborne transmission, albeit under carefully controlled laboratory conditions (see "Transmission of Ebola virus from pigs to non-human primates," in Scientific Reports).So is it likely that the airborne transmission of Ebola will occur? Not really -- not at this point -- but the longer we take to bring this current outbreak under control, the greater chance of something like this happening.Ebola is nasty, and evolution can be, too.

The transmission reports you note are not airborne transmission; they're transmission by droplets of body fluids. That might seem like a pedantic quibble but it really is a fundamentally different thing. Body fluids can be transmitted short distances as droplets - of courser they can - but since Ebola does not cause coughing or sneezing it's relatively unlikely to spread far by this means and this means, in any case, doesn't allow the virus to rapidly circulate in shared airspaces in the manner of the cold and flu viruses spread by aerosols.As for the ferret experiments; this is mutation of existing mechanisms of airborne transmission for a new host not de novo transition to airborne transmission.It is, of course, technically possible that Ebola can mutate in this way but it's not any more likely than rhinovirus mutating to cause bleeding from every orifice and subsequent death.

10,000 people is not the 6 billion person human population. In this scenario, you would have 9,000 dead. In this scenario, you have 1 million dead which is several orders of magnitude higher than scenario 1. I would personally think that 1 million dead is more worrisome than 9,000 dead.What I am trying to contrast is the mortality rate vs. the rate of infection.

Someone said that they were more worried about the mortality rate than they were the rate of transmission. I was trying to contrast the two, showing that a virus with a much lower mortality rate but higher rate of transmission will cause more deaths.

It all depends on publicity and who are the 1 million dead?

It also depends on who feels threatened. WHO reported that over 400,000 people died from malaria in 2012 alone, and possibly as many as 800,000. They considered that a good year."About 3.4 billion people — half of the world's population — are at risk of malaria. In 2012, there were about 207 million malaria cases (with an uncertainty range of 135 million to 287 million) and an estimated 627 000 malaria deaths (with an uncertainty range of 473 000 to 789 000). Increased prevention and control measures have led to a reduction in malaria mortality rates by 42% globally since 2000 and by 49% in the WHO African Region."
Malaria More people die of malaria every year than have died from Ebola in all of the modern age.

What IS passed on is if you are someone who is resistant to a disease, you pass on your resistance to your descendants.

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Someone said that they were more worried about the mortality rate than they were the rate of transmission. I was trying to contrast the two, showing that a virus with a much lower mortality rate but higher rate of transmission will cause more deaths.

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But that's not what you did. You contrasted the total number of infected, rather than the rate of infection. As long as the reproduction rate is greater than 1, the epidemic is going to continue growing; all the transmission rate affects is how quickly it grows. An epidemic that doubles in size every week will infect the entire planet in 8 months. An epidemic that grows at 1/4 the speed will take 2.5 years -- but everyone still gets sick.That's why we're worried about Ebola. It's not how many are currently infected -- it's the possibility that it's going to keep growing, with no obvious end in sight.

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What IS passed on is if you are someone who is resistant to a disease, you pass on your resistance to your descendants.

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Sometimes.