A New Origin Story
Online Science Editor Vincent Plant discusses a new study on the origins of the measles virus
Measles is a virus that is regularly shrugged off in this country; however, it is not to be taken lightly. The WHO estimated that 142,000 died due to this disease worldwide last year. As such, there is a big incentive for us to understand more about measles and its impact on humanity. Now, an international team of scientists have worked out when exactly it leapt into our lives.
Measles is a zoonotic virus, meaning that it crossed the species barrier to infect humans. We previously knew that it evolved from rinderpest, a virus found in cattle which was a persistent problem until vaccination programmes eliminated it in 2011. Such transitions are quite a common phenomenon, with the origin of the recent COVID-19 pandemic being a case in point. However, there are many other examples, including bird and swine flu.
Measles… crossed the species barrier to infect humans
As such, we knew that measles had its origins in cattle. However, we couldn’t pin down the exact time frame. Previous analyses gave us a ballpark figure of around 900 AD, but this used recent measles viruses. A new study used virus samples found inside the lung tissue of an individual who died from the disease in 1912. From there, researchers compiled a family tree by comparing it with more recent strains, rinderpest, or a related virus which affects sheep and goats. This dated the jump to 500 BC – twelve centuries earlier than average figures previously indicated.
This still doesn’t tell us precisely where the jump happened, but we can make some inferences. For instance, the measles virus cannot survive in any community which is smaller than half a million people, because of the fact that it causes lifelong immunity – enough babies are born to fuel the virus only in populations larger than this. At roughly this same time, we see cities with hundreds of thousands of people beginning to rise up in India, China, and the north of Africa and Europe. It is therefore quite possible that one of these communities fuelled the rise of measles.
The measles virus cannot survive in any community which is smaller than half a million people
Understanding how diseases arose could be critical for understanding new outbreaks, such as in the case of the coronavirus. In reshaping our understanding of when it evolved, we’ve just got one step closer to fully comprehending measles.
