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Ebola outbreak

# Understanding R nought

Dr. Rishi Desai is a pediatric infectious disease physician and former epidemiologist with the Centers for Disease Control and Prevention (CDC).

## Want to join the conversation?

• At the end, Dr. Rishi said that for measles, you can take a vaccine (MMR) to prevent getting measles, but is there a vaccine for Ebola?
(1 vote)
• hopfully they will find a vaccine soon for ebola
• What's the R and o in Ro? Also what's the R in R nought?
• Are there any diseases that have R nought 0? I don't mean eradicated diseases but current diseases that everyone has a vaccine for it.
• There is only one eradicated disease known to mankind so far---smallpox, with polio being a possible second sometime in the future. But to answer your question, yes, there are probably some obscure diseases with R0=0, but they have most likely all died out or will do so soon. However, technically, cancer or things like heart disease or mental illness have R0=0-<1. (Depending on genetic transmission)

As for the second part of your question, vaccine alone cannot ensure that the R0 becomes 0, because it would be very difficult to vaccinate every single person who could possibly be infected by the disease. Even the eradication of naturally-occurring smallpox did not result from global vaccination, although it was considered a possible strategy and attempted.
• It seemed that example D was the most infectious, but I just realized that the infectious period is also a factor. So measles, with R0=18, in WEEKS, is not necessarily as infectious as Ebola, with R0=2, in DAYS. Am I correct to come to this conclusion?
• Right. If you assume 1 day for C and 1 week for D, C will spread to an average of 18 people in a week, while 2^7 people, or 128 people, will be infected by each original case for D in a week, on average.
(1 vote)
• what does R-NOUGHT mean?
• What is the period of time needed for R nought? as There can be a difference between Decades and weeks when calculating it.
(1 vote)
• You can make up the period of time for the R nought. For example, the R nought could equal 7/4 in 2 weeks, or 92/13 in 15 months. If you want to get two different periods to be the same, you could just divide one of the bigger numbers.
• If the Flu has a nought of 2, and other diseases have higher numbers (like measles has 18), then why is the flu more common than any of those other diseases?
• I'd say it's more common because of how easily you can get it; you can get it just from breathing it in.
• Lets say we had 10 people infected with Ebola, after a couple of weeks there would be 5 newly infected people, so, R0 would =2, and the disease would be spreading from person to person. Am I right?
(1 vote)
• R-Nought is how many people each person will probably infect. So if you started with 10 people, you would expect to have 20 new cases after a couple weeks (so you would have 30 cases total).