Yes I maintain the site. I'm totally open to adding more states/locales, but I do not have the time to go through each state's data source. As I mentioned in the footer the data comes directly from the Florida Department of Health, there isn't a more official source for county-level data than that. If any other developers would like to add other locals, please submit a PR on the GitHub repo. If you know of an API that gives out county-level data for the entire country, I would love to use that instead. :)
Oh... I did not even see this was even more limited to Florida only! Really, you should first ask for help on English Wikipeia at least to see if you get support for extending it to other US states, and possibly other countries. But I bet most won't be interested as Wikipedia already has a more complete dataset (and accurately checked, with all sources compared, not just one which uses one state-level method, and not the exclusive one at federal or international level). You should know that such statistics is highly sensitive to the methodology used, and there are many criterias (the WHO site gives some hints about their varaibility and what they are about, there's no single way to count things, including in one given country, and governmental sources are not always accurate on everything, frequently with underestimates!)
Such project is in fact not maintainable by a single person from his chair at home, it absolutely requires huge cooperation, at nation and international scale and requires monitoring as well other indicators. Even Google renounced to do that itself ! The best you can do however is to help the Wikipedia project if they are missing some data sources, in order to collect and track more (you MUST absolutely give the sources, as many sources use different methods or may be out of sync with others, using different time-frames for their measurements, and also frequently correcting their figures later).
Then you can use the data collected in Wikipedia and Wikidata to make a translatable app if you wish (exactly what Google did itself!).
English Wikipedia, nor Wikidata, maintain county-level data which is necessary to preform the calculation.
I'm not sure why I have to defend an applicaiton I wrote. If you don't want to translate the 7 strings, then just say so.