Spanish Flu: a warning from history

The Spanish Flu, often called a 'forgotten pandemic', was a massive global calamity, killing an estimated 50 to 100 million people – far exceeding World War I casualties. Originating around May 1918, it swept through the US, Europe, and the trenches. It was dubbed 'Spanish flu' by the neutral Spanish press. Initial estimates of 20 million deaths increased to 25 million by the late 20th century, and now range from 50 to 100 million in the 21st century after closer scientific and historical collaboration.

Scientists are still unsure why some flu strains are more severe. Avian and pandemic viruses replicate deep in the lungs, triggering a strong immune response. This leads to an influx of white blood cells and fluids, restricting air space. Symptoms were graphic: people 'drowned in their own phlegm,' spurted blood from ears and noses, and turned blue or purple. Unusually, victims were primarily 20-40 years old. Deaths occurred from the initial infection or an overwhelming immune response causing fluid in the lungs.

While conditions in the trenches are often cited, the rapid global spread suggests other factors. The traditional explanation is an origin in a Kansas army camp, with troops bringing it to Europe. However, many unknowns remain. Mathematical models attempt to untangle its global spread and routes. Understanding the origin could help prevent future pandemics. It was almost certainly initially a bird flu, also present in pigs. The key question is how the virus adapted from an animal (avian or swine) virus to a transmissible human virus, undergoing rapid evolutionary changes within an infected person.

Just as people celebrated Armistice Day, a far more deadly and virulent second wave emerged, spreading like wildfire and affecting a third to a quarter of the world's population. Though short-lived, petering out by 1920-1921, the virus continued to transmit among humans until 1957, adapting to humans rather than remaining an avian or swine virus that was accidentally pathogenic.

Researchers are studying flu evolution to predict its future changes and create effective vaccines, artificially evolving the virus in labs and computers. They also investigate how the virus transforms in birds and other species to protect against future variants. Flu is difficult to eradicate due to constant mutation, specifically focusing on the enzyme that copies its genetic information and how it introduces mutations leading to new strains and triggers immune responses.

Scientists are deeply concerned about another pandemic as deadly as 1918's. The UK's national risk register places an influenza pandemic alongside a terrorist event as the most catastrophic. Highly pathogenic H5 and H7 flu viruses have already infected and killed many. If these viruses adapt for efficient human-to-human transmission, they could be as devastating as 1918. Experts believe it's 'not if, but when' a new pandemic will occur. Studying the 2009 pandemic data helps understand spread and allocate resources for future control. The hope is that within 10-40 years, improved surveillance, drugs, vaccines, and knowledge of viral weaknesses and immune systems will lead to a universal flu vaccine.