Special Report

How Bad Is the Flu Season in Every State?

Detailed Findings & Methodology

Relatively high numbers of cases have been reported in most of the country. New York City, Puerto Rico, and 32 states reported high flu or flu-like illness activity. Every state except for Hawaii had widespread influenza activity as of the second week of January.

CDC epidemiologist Lynnette Brammer, in an interview with 24/7 Wall St., noted activity levels could be from illnesses other than the flu. However, “you don’t get to high [flu activity levels] with something other than influenza,” she added.

The flu activity levels listed here are relative to what you would expect them to be if flu were not circulating. Flu seasons vary considerably, however, and a host of factors make mapping the spread and intensity of influenza in order to compare states a surprisingly difficult task.

“I’ve been doing this for more than 20 years and I can’t tell you why in a given year one state gets hit really hard and another one doesn’t get hit as hard,” said Brammer.

To identify the incidence of the flu in every state, 24/7 Wall St. reviewed the latest weekly influenza surveillance report prepared by the influenza division of the CDC. Influenza-like Illness activity levels (minimal, low, moderate, and high) are based on the difference between current and off-season average proportions of outpatient visits to health providers for flu-like illnesses. It is important to note that outbreaks occurring in a single city could cause a state to display high activity levels, and data collected may disproportionately represent certain populations within a state and therefore may not accurately capture influenza activity for the whole state. The percentage of patients with flu-like illnesses so far this flu season (October 1, 2017 through February 3, 2018) was calculated by 24/7 Wall St. using data reported weekly to the CDC.

Activity levels for states are measured against regional average patient visits for flu-like illnesses. Across the 10 regions, these baselines range from 1.3% of patients in the Denver region (Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming) to 4.2% in the Dallas region (Arkansas, Louisiana, New Mexico, Oklahoma, and Texas).

Each state’s 65 and over population was obtained from the U.S. Census Bureau’s 2016 American Community Survey. The number of primary care physicians for every 100,000 people in each state came from County Health Rankings & Roadmaps, a collaboration between the Robert Wood Johnson Foundation and the University of Wisconsin Population Health Institute.