As the Centers for Disease Control and Prevention (CDC) are warning that more and more states in the country are reaching “Widespread” influenza activity, let’s look back at where we were one hundred years ago with regards to influenza. As you may know, the world experienced a severe pandemic (worldwide epidemic) of influenza in 1918. The exact origin of the pandemic is not known, but there are strong indicators that it started in Kansas and then spread around the world as American soldiers traveled to fight in World War I. By the end of 1918, millions around the world had contracted the disease, with between 20 and 50 million people dying from it.
But what about 1919? That year brought with it a third wave of pandemic influenza. While it was not as explosive or deadly as the first and second waves, it still caused a lot of disruption and deaths. In Mexico, for example, the third wave lasted from January to June of 1919, influenza may have killed up to 100,000 people. In Great Britain, the third wave lasted from February to April, killing up to 10 people per 1,000 residents at the peak in early March of 1919. Over in Paris, President Woodrow Wilson of the United States fell ill to the flu as he was in Europe to work on post-war issues with the Europeans.
There is some evidence that the deadly H1N1 influenza that brought the 1918 pandemic started circulating in 1915, but it did not “shift” its genome until late 1917. By 1918, whatever its origin was, the influenza virus was able to cause disease in a very big segment of the population. It caused so much death that the life expectancy in the United States and the rest of the world dropped by several years. The pandemic didn’t happen overnight.
Currently, there are several influenza surveillance systems up and running all over the world. In the United States, CDC coordinates with state and local health departments to collect health data in order to understand where and when influenza is active. It used to be that these systems all required some sort of contact with healthcare by the people sick with influenza (or influenza-like illness, ILI). More recently, “participatory epidemiology” has allowed epidemiologists to receive information from the public on whether or not they (the public) are feeling influenza-like illness symptoms. (For example, there is Flu Near You, which you should check out.)
An important part of these influenza surveillance systems are laboratories where human samples are tested for influenza. The viruses that are isolated and identified are then fed into a stream of information to make sure that the current and future influenza vaccine will be a good match. This is not an exact science, as recent vaccine mismatches have shown, but they’re still the best way to make the best choice in which vaccine to use and where to use it.
The other big part of these surveillance systems comes from information gathered on people who get so sick that they need to be hospitalized or, unfortunately, die from influenza. This information is crucial to public health so messaging about influenza prevention can be tailored to those most at risk for severe complications. For example, during the 2009 H1N1 Pandemic, it became clear that pregnant women and morbidly obese persons where at high risk for hospitalization and/or death. As a result, pregnant women were moved to the front of the line when it came to vaccine administration at a time when the vaccine was in short supply. Similar decisions made by healthcare providers on an individual patient basis would be informed by the epidemiology of the disease, and that epidemiology would be informed as well by the surveillance systems in place.
The big lesson from the 1918 pandemic was that we all need to be prepared for an influenza pandemic that may infect a large segment of the population, disrupting delivery of goods and services. Another lesson is that it took time for the pandemic to develop. It didn’t happen overnight, and it happened at a time when mass communications were not as widely available as today. In 2019, we need to be prepared to collect as much information on influenza – and other diseases – and be ready to analyze it and disseminate findings. There are going to be big decisions to be made by public health authorities and healthcare providers, so they need to be informed with the best available epidemiological information.