You may remember the H1N1 “swine flu” that emerged in 2009. While the seasonal flu normally leaves a patient miserable for a week or two, the swine flu killed over 12,000 U.S. citizens and an estimated 575,000 worldwide.
Few, if any, would remember the Spanish flu pandemic that occurred 100 years ago. Infecting approximately 500 million, it devastated the entire world, killing approximately 50 million people from 1918 to 1919. In a single year, the Spanish flu killed more people than four years of military and civilian casualties in World War I.
Perhaps one of the most terrifying trends of the 1918 flu season was that it not only claimed the lives of the young, the elderly, and the immunocompromised, but also of seemingly healthy adults, with an overall mortality rate of 10-20% of those infected. Nearly a third of the world’s population became infected with this pandemic, leading to a decrease of nearly 3-6% of the world’s population. It is thought that some of the deaths could have been due to excessively large doses of aspirin that was commonly administered at that time. Also, the lack of antibiotics to treat secondary bacterial infections contributed to a high mortality rate.
The first case of the Spanish flu in the United States was recorded on March 11, 1918, by a soldier in Fort Riley, Kansas. Within hours, soldiers in close quarters were dropping like flies. Patients experienced sudden onset and suffered from fever, gastrointestinal illness, and hemorrhaging. Many fell victim to viral pneumonia and pulmonary edema. The second and deadliest wave began in September 1918 in Boston. While World War I was coming to a close, the disease spread like wildfire through Western Europe, Russia, East Asia, and North Africa. Due to high demand, cities ran out of coffins and resorted to mass graves. The flu saw no boundaries; even the king of Spain, Alfonso XIII, and U.S. president, Woodrow Wilson, fell ill. The third wave started in January 1919, when it finally reached Australia, but it exhausted itself by the summer.
Public health authorities of the day remained baffled at the causative agent of the Spanish flu. Doctors attempted administering streptococcal, pneumococcal, and Haemophilus influenzae vaccines that proved useless. Some tried rinses with various chemicals, including sodium bicarbonate, boric acid, and hydrogen peroxide. Rural folk remedies involved goose grease poultices and a
diet rich in onions.
The American Public Health Association
advised good hygiene, such as washing hands and preventing sharing of silverware. Schools and businesses were shut down, libraries stopped lending books, and spitting was banned to prevent transmission of the disease.
Fast-forward 100 years, with the help of molecular biology and knowledge of epidemiology, scientists can trace back the origins of the Spanish flu. The “Spanish flu” is a misnomer in itself; it first hit America, Europe, and Asia in the spring of 1918. While other countries suppressed media coverage of the pandemic, not wanting to show weakness to the enemy during WWI, Spain (being neutral) did not. When the illness made the headlines in May of 1918, Spain took the blame.
On a molecular level, this particular strain is thought to have been derived from an avian influenza virus. RNA sequencing shows that it entered the human population in approximately 1915 but did not cause significant disease until 1918. Still, humans had not been exposed to this strain, which resulted in a particularly deadly epidemic, in part due to its ability to infect and cause substantial damage to the lungs via a “cytokine storm” triggered by an overactive immune response.
Though the 2009 swine flu is colloquially known as “H1N1,” the Spanish flu is also subtype H1N1. The term H1N1 refers to the type of hemagglutanin “HA” and neuraminidase “NA” proteins that identify type A influenza viruses. Type A influenza viruses are found in pigs, domestic poultry, wild birds, and other animals. Type B viruses, which are classified by lineage rather than subtype, infect humans along with type A viruses, but do not infect animals. Other type A viruses of concern include H2N2, H5N1, H7N9, and this most recent season’s H3N2 virus. The H1N1 influenza virus that made the jump from birds to humans in the early 20th century continued to circulate in humans and currently resides in pigs. Now, the H1N1 Spanish flu has four descendants; two H1N1 and two H3N2 viruses.
There is no doubt that the Spanish flu was a tragic event that rocked the world, but the damage has been done. The influenza virus still circulates, rapidly mutating, but humans now respond by producing a vaccine every year. Flu vaccines are trivalent, meaning they immunize against a type A H1N1 virus, a type A H3N2 virus, and an influenza B virus. These are the strains most commonly spread through humans. A hundred years ago, the world was not so fortunate to have developed a flu shot; far fewer could have suffered if there was. They have truly revolutionized the healthcare industry and have saved billions of lives. While success rates of influenza vaccinations have been reportedly lower than desired (40-50%) due to the uncertainty of predicting which strains will be prevalent in any given year, you can bolster the protection of yourself and the people around you by getting vaccinated at a doctor’s office or local pharmacy, as the flu vaccine has been reported to decrease the severity of the disease, even if it is unsuccessful in preventing it.
While the most recent flu strains have not been as virulent, the vaccination and good hygiene are the best way to prevent illness for those at increased risk of complications due to influenza complications, such as young children, the elderly, and the immuno-compromised. In 1918, the combination of virulence and lack of immunization killed 50 million people. In 2018, we have the tools to prevent another devastating flu epidemic.