Florida, Arizona, and Texas have all received extensive news coverage as recent coronavirus hotspots. Looking at the COVID-19 case data, it’s easy to see why. Each of these states saw a dramatic increase in new COVID-19 cases over the course of June and into July (see Figure 1).
But although the recent trends have been concerning in all three states, Kinsa’s early illness data suggests that these states may follow different trajectories in the weeks to come. In particular, the outlook doesn’t look good for Florida and it looks even worse for Texas. Arizona, on the other hand, is showing some encouraging early signs of slowing illness spread.
A disease’s effective reproductive number, Rt, is a critical metric used to understand whether an illness outbreak is under control, with values above 1 indicating that an uncontrolled outbreak is likely, whereas values below 1 indicate that an outbreak is less likely to grow.
Kinsa uses hyper-local fever data to derive our own real-time measure of Rt for flu-like illness (including COVID-19). By comparing it to typical seasonal trends in a given local area, we can identify areas with unusual disease spread, or “atypical Rt”. Kinsa’s atypical Rt measure is a three-week leading indicator of COVID-19 case growth.
Looking at Kinsa’s recent Rt data, we see an incredibly concerning picture for Texas. While the rate of illness spread has exceeded 1 at times over the past month in many states, Texas’ rate of illness spread has significantly exceeded 1 for the entirety of the past 30 days. This level of sustained, rampant disease transmission suggests that there is likely a lot more illness in the community than what has been reflected in the case numbers to date. In other words, there is no relief in store for Texas over the next few weeks, and we fear that the situation there may get much worse in the near-term.
Florida’s trend is also concerning. After a brief slowdown in the third week of June, the rate of illness spread began rising again on June 25th and has hovered around 1 ever since. This suggests that community illness transmission continued unabated over the past few weeks, and as a result, the state has likely not yet hit its peak in the current wave of the outbreak.
In more encouraging news, Arizona looks to be headed in the right direction. The rate of illness transmission has been trending downwards ever since the Governor paused the state’s reopening plans at the end of June, suggesting that mitigation efforts, are beginning to reduce the rate of community transmission.