The Spanish flu pandemic of 1918, the deadliest in history, infected an estimated 500 million people worldwide—about one-third of the planet’s population—and killed an estimated 20 million to 50 million victims, including some 675,000 Americans. The 1918 flu was first observed in Europe, the United States and parts of Asia before swiftly spreading around the world. At the time, there were no effective drugs or vaccines to treat this killer flu strain.

According to Monmouthshire medical officer Dr David Rocyn-Jones, the epidemic "spread with alarming rapidity". Dr Rocyn-Jones - a former doctor and colliery surgeon in Abertillery - said the infection generally attacked men working in the pits, followed by the mothers and older children "and finally the children attending the infant schools".
The Abertillery Medical Officer of Health blamed the spread of infection on overcrowded and unclean railway carriages, crowded taprooms, local picture houses or cinemas, and the damp conditions of the coal and tinplate works. He cited 32% of the male population and 25% of the female population in the Abertillery district were affected.

Across the county, measures were put in place to prevent the spread of infection – All Sunday Schools were closed, all children under the age of 14 were excluded from attending cinema performances and all schools in the county were closed from 3rd July to 12th August.

By the time the schools opened again in September 1918, the number of cases had dropped considerably, but a second wave of cases was soon to follow.

However, a second, highly contagious wave of influenza appeared with a vengeance in the fall of that same year. Victims died within hours or days of developing symptoms, their skin turning blue and their lungs filling with fluid that caused them to suffocate. In just one year, 1918, the average life expectancy in America plummeted by a dozen years.