No, Seriously, How Contagious Is Ebola?

That first reaction was understandable. There's no question the disease is scary. The World Health Organization now estimates that the virus has killed about 70 percent of people infected in West Africa.

The Ebola case in Dallas is the first one diagnosed outside Africa, the Centers for Disease Control and Prevention said Tuesday. And the health care system in Texas didn't quarantine the man right away. He was sick with Ebola — and contagious — for four days before he was admitted to the hospital.

But when you look at health officials responding to the case in Dallas, they seem cool as cucumbers, despite the initial misstep.

"I have no doubt that we will control this importation, or case, of Ebola so that it does not spread widely in this country," said the director of the CDC, Dr. Tom Frieden.

The reproduction number, or "R nought," is a mathematical term that tells you how contagious an infectious disease is. Specifically, it's the number of people who catch the disease from one sick person, on average, in an outbreak.*

Take, for example, measles. The virus is one of the most contagious diseases known to man. It's R0 sits around 18. That means each person with the measles spreads it to 18 people, on average, when nobody is vaccinated. (When everyone is vaccinated, the R0 drops to essentially zero for measles).

At the other end of the spectrum are viruses like HIV and hepatitis C. Their R0s tend to fall somewhere between 2 and 4. They're still big problems, but they spread much more slowly than the measles.

And that brings us back to Ebola. Despite its nasty reputation, the virus's R0 really isn't that impressive. It typically sits around 1.5 to 2.0.

Even in the current epidemic in West Africa, where the virus has been out of control, each person who has gotten sick has spread Ebola to only about two others, on average.

Many factors contribute to the R0, such as how long you're infectious** and how many virus particles are needed to make another person sick.

But in Ebola's case, the mode of transmission probably helps keep its R0 low. Ebola isn't spread through the air, like the measles or flu. It requires close contact with some bodily fluid, such as blood or vomit, containing the virus.

Now at this point, you're probably thinking, "OK. But an R0 of 2 is nothing to brush off." You're right. R0 of 2 means one person infects two people, who then infect four people, then eight, 16, 32 — the numbers go up fast.

But that isn't likely to happen in a place with a good public health system, like the U.S. Why? Because people with Ebola aren't contagious until they show symptoms.

So to stop the chain of transmission, all health workers in Texas have to do is get the people possibly infected by the sick man into isolation before these people show signs of Ebola.

Then R0 drops to zero. And Texas is free of Ebola.

*We're talking the "basic" R0 here, for all you epidemiologists. So, the R0 that you get when everyone in the population is susceptible to the disease.

**The R0 is integrated over the time that a person is infectious to others. For HIV, this could be years. But for Ebola, that time is only about a week. So even though they have similar R0s, Ebola's infections per unit of time is much higher than HIV's.

This chart looks calming until you are the one that has been exposed to another that was exuding blood from every orifice. Rabies is hard to get but once the disease is showing symptoms you may as well kiss it goodbye. Ironic that if a person is exposed to a rabid animal we begin prophylaxis right away.

No virus has ever been known to mutate.

No virus that has a 70% kill rate within a few weeks of infection has ever been viewed as a serious public health risk that required quarantine.

(Sarcasm tag implied for the sarcasm impaired.)

This is so BS. This is just anecdotal maybe based on official counts and we all know for every person who dies in the hospital at least one is dying in the bush.

If they are looking at past outbreaks what they say might be true they were short and contained but this epidemic shows no signs of stopping because they don’t have enough medical help and they are backward people.

So...if it can be bad in the bush then it could grow exponentially in a crowded city.

Not everybody runs to a hospital or doctor at the first sign of an illness. Many will get up and go to work anyway.

Now it is easy to tell who may have it because they have all recently come from Africa but let a few cases get away and it is a crap shoot.

Frieden is an idiot. Now that we’ve got that out of the way, my question is,”WHY DID WE HAVE TO BRING EBOLA TO THE U.S. IN THE FIRST PLACE?” Ebola was doing just fine when it was ONLY in Africa. What it is the commie libs like to say? “If we can save just one child?” When adults were running this chicken coop, they would have done everything in there power to keep the crap out of here. Now we have moronic liberals saying we owe it to the Liberians to bring Ebola here because their ancestors were former slaves in the U.S. The lunatics are running the asylum.

Before Obama started importing it into the US, the government considered it to be the boogeymen of diseases, the “mostest-horriblest” disease on the planet. And we paid big bucks for research on it, because we were told that if just one case made it to the western hemisphere, then its game over!

Today, it’s just a bad cold. Nothing to worry about.

Were they lying then or now? Or both?

Well, Michaeleen, I’m glad to know that you won’t worry
when you find out you’ve been carried in an ambulance
that just carried an Ebola patient.

NPR, did you think they were going to do anything
besides soothe the proles?

Zaire does mutate slightly between different clusters, but the mutations, usually found through dna testing, have little or no effect on the virus strain, which is resistant to exchanging RNA with other viruses.

From what I have read, this is due largely to space requirements within the containment envelope of the virus which is a specific size and shape.

Having said that, mutation of a strain changing kind is certainly a worry and the chances are not zero..and rise with the total number of infected who pass it on.

Devil’s advocate...

If I’ve got the mumps, I’m infectious for around 25 days...and its not usually deadly, so ,ost people around me won’t be wearing moon suits.

If I’ve got Ebola, as soon as I’m diagnosed, I am quarantined and only people in protective gear will come near me. IOW, my period of being contagious has been interfered with.

So, any conclusions based on looking at this R0 are somewhat flawed. People with Ebola infect fewer people than the mumps...because people are scared to death of getting Ebola.

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