Everyday Statistics, with Eddie Davila

- [Eddie] Between 50 to 100 million deaths, or, about three to six percent of the world's population. That's how many people are estimated to have died from the 1918 global flu pandemic. That was back then, but even today, the flu can be deadly. During the 2017-2018 flu season, it is estimated that there were about 80,000 deaths in the US related to the flu. It was considered one of the deadliest flu seasons in the last few decades.

The field of medicine has gotten better since 1918. The utilization of statistics has also helped us combat the flu. The flu is not a single disease, but rather, multiple viruses with multiple strains. To complicate things, these viruses change year to year, and each year, different flu viruses are more prevalent than others. To help people avoid the flu, each year, flu vaccines are created and administered, but creating and distributing these vaccines takes about six months.

These vaccines can't cover all the possible flu viruses, especially since during those six months, some of the flu strains might change, and the vaccine might become ineffective in fighting that strain. So, how are statistics a useful weapon in fighting the flu? In the US, during the month of February, the Food and Drug Administration determines which three or four flu viruses will likely be the biggest threats in the next flu season. This decision is based on patient data that is continuously gathered from around the world, statistical forecasts of how these diseases will likely spread, as well as the analysis of test results on virus samples gathered from around the world.

In September, as the flu season approaches, the vaccines are finally ready to be administered. At this point, scientists also have a better idea of how effective the vaccine is likely to be that season. Some years, the vaccine can reduce the chances someone will get the flu, by 40 to 60 percent. In other years, it's much lower. For example, during the 2014-2015 flu season, the vaccine was only about 19% effective.

The prevalent flu that year changed so much that the vaccine was not helpful in preventing that particular strain. Luckily, that was not as deadly as the strain of the 2017-2018 flu. During the flu season, as that season's dominant flu virus begins to spread, statistics help uncover the present and future needs. Which age ranges are the most susceptible to that year's flu? What's the rate of hospitalization, an unfortunate indicator of the likely death rate? Data from hospitals, health clinics, and government health departments around the country are continuously analyzed.

For doctors, pharmaceutical companies, global health organizations, and epidemiologists, understanding averages, medians, probabilities, and confidence intervals can be a primary weapon in helping to fight the flu, and other diseases.