Don’t only look at Ro numbers
Recently in class, we’ve been learning about how to calculate the basic reproductive number and use it to interpret epidemic possibilities. However, when looking at RO numbers, we should be careful of what we are actually interpreting and what we should be worried about and what we shouldn’t. First, the issue of looking at RO number we need to be aware that this number can be calculated for everything, not only diseases, especially dangerous ones. When we hear the word epidemic, our minds automatically associate it with terrible illness. For example, in the article above, it mentioned that the RO of the ebola epidemic in 2014 was between 1.5 and 2.5 while the RO of the measles epidemic in 2014 was between 12 and 18. Despite these numbers, ebola commanded the headlines of newpapers and televised news. This is because RO is not the only number taken into consideration when we look at the risks of a disease. Measles was indeed more contagious than ebola but it was also more treatable. Few people could actually die from contracting the disease. Ebola, on the other hand, had lower contraction rate but higher death rate due to lack of vaccinations available as well as treatments.
The article also mentions how the basic reproductive number, RO, relates to vaccinations. As a reminder, as we learned in class, the threshold for whether an illness would become an epidemic is RO =1. Thus, when calculating the minimum number of people that needs to be vaccinated for the illness to eventually die out, we must have a RO of less than 1 after vaccinations. The article mentions that proportion of population to be vaccinated would be equal to 1-1/RO. This makes sense as the greater the RO, the more people there would need to be vaccinated to bring the RO to 1.
Lastly, the article also mentions another issue of looking at RO in terms of real life examples: location. RO of certain diseases in developed countries would definitely be lower than in developing countries due to better healthcare and greater access to vaccinations. Thus, whenever we look at an RO number, we should make sure to check what disease it is for, where the disease is centralized, and what current treatments and vaccinations are available are there for it before we start worrying.
https://blogs.scientificamerican.com/roots-of-unity/understand-the-measles-outbreak-with-this-one-weird-number/