The order of spread

THE RULES OF CONTAGION IS LESS ABOUT DISEASES AND MORE ABOUT THE UNDERLYING PRINCIPLES OF CONTAGION

- ANSHIKA RAVI

THE PERPETRATOR of The Rules of Contagion is not the COVID virus the world cannot stop talking about. Written by epidemiologist and mathematician Adam Kucharski’s contagion transcends the realms of biology and deep-dives into social and behavioral norms and narrates how similar rules can be applied to the disparate worlds of finance and social media. The hero of the book is Ronald Ross, a British doctor, who discovered that malaria is caused by mosquitoes. A journey that spanned over 50 years—during which he also won the Nobel Prize—Ross turned to mathematics to find the answer to a very pertinent question: how to control the spread of malaria without eliminating every mosquito.

Ross made some crucial discoveries that revolutionized how the world looked at contagion. For example, he found that even if there were 48,000 mosquitoes in an area, on average, they would lead to only one human infection. That is, the disease would fade out if the mosquito populations were reduced below a critical level. It would take many more years for the world to fully adopt mosquito control. “The world requires at least 10 years to understand a new idea, however important or simple it may be,” Kucharski quotes Ross.

His indignation was probably not uncalled for: He did not live to see all his ideas translate into practice. But more than a century later, we continue to borrow his methods—to study the spread of loneliness and obesity as much as infectious diseases. Ross’ mosquito discovery paved the way for another interesting question: what causes epidemics to end?