Epidemiologists, the people who study contagious diseases, believe that influenza is the greatest contagious disease threat to humans. The reason for that belief is that influenza viruses change continuously making it difficult to formulate a preventive vaccine or a cure for the disease. The plague pandemic that occurred in the 1300s killed the highest percentage of its victims in the recorded history of contagious disease. But influenza is a serial killer that reappears every year. The influenza pandemic of 1918 killed an estimated one hundred million people.

Two factors make influenza a serious threat. First, the population of world is more than seven billion people. We live in close proximity, and we travel continuously making it possible for a contagious disease to spread rapidly.

Secondly, influenza viruses have a unique reproductive process that makes them dangerous. The virus cannot reproduce by itself. It must invade a human cell or a cell of another animal. The virus can then commandeer the cell’s biochemical processes to reproduce itself in very large numbers and very quickly. The regulatory process provided by DNA that governs reproduction in most species is missing in the influenza virus. A significant percentage of the offspring are defective and unable to function. But that same unregulated process also produces new variations of influenza viruses for which existing vaccines aren’t effective. Vaccines have to be reformulated almost every year to keep up with the mutations. But wait; there’s more. Two viruses can invade the same animal cell. When that happens, the viruses can exchange genetic material and produce a new influenza virus for which humans have no immunity. That may be what caused the 1918 pandemic.

Historically, contagious diseases have often been fatal to children whose immune systems are not fully developed or to elderly people or to those whose immune system has been compromised by other illnesses. But the 1918 influenza pandemic’s prime target was healthy adults aged 25 to 29 and, especially, pregnant women. Some scientists believe that the strong immune systems of healthy young adults overreacted to the new alien virus adding to the damage. Some victims, who might have survived the influenza attack were so severely weakened that they succumbed to pneumonia infections.

The effectiveness of influenza vaccines varies from year to year and among age groups. However, the U.S. government’s Centers for Disease Control and Prevention recommends that most of us should get an influenza vaccination every year. Even during a year when the vaccine isn’t particularly effective, it can still protect millions of people and disrupt a potential epidemic. There is no medicine that will cure influenza.

During the peace treaty at the conclusion of World War One, the French and English were bent on revenge. America intended to moderate that desire for revenge and promote a genuine peace. But America’s representative at the peace conference, President Wilson, contracted influenza during the conference and was unable to function effectively. John Barry writes in The Great Influenza: “Historians with virtual unanimity agree that the harshness toward Germany of the Paris peace treaty helped create the economic hardship, nationalistic reaction, and political chaos that fostered the rise of Adolf Hitler.”

Jack Stevenson is retired, served two years in Vietnam as an infantry officer, retired from military service, and worked three years as a U.S. Civil Service employee. He also worked in Egypt as an employee of the former Radio Corporation of America (RCA). Currently, he reads history, follows issues important to Americans, and writes commentary for community newspapers.