Earlier this month the North Carolina Department of Health and Human Services issued an update to its ongoing investigation into an outbreak of Legionnaires’ disease linked to a hot tub display at the North Carolina Mountain State Fair. At the time, health officials knew of 134 confirmed cases, including 88 individuals who needed hospital care and two deaths.

Things haven’t exactly improved in the week since that bulletin was issued. Just a couple of days ago, the NCDHHS provided another update to the statistics, this time noting a total of 142 confirmed cases of the disease, including 95 hospitalizations and 2 additional deaths, bringing the death toll to 4.

This whole saga began when a hot tub at the fair apparently became a breeding ground for Legionella bacteria. This isn’t unheard of, as hot tubs have been known to foster such bacteria, but the fact that it happened in a location with heavy foot traffic was a worst-case scenario. The bacteria can live in the tiny water droplets and mist produced by hot tubs, and as fair-goers walked by the display they unknowingly put themselves at risk of falling ill.

Those who attended or worked at the fair began falling ill within two days, and it didn’t take health officials long to draw a link between all the cases. They quickly narrowed down their search for the source due to the fact that there were no other possible avenues of contamination.

Symptoms of Legionnaires’ disease — and the closely-related but less-severe Pontiac fever — include fever, headache, nausea, and vomiting. In Legionnaires’ disease, those symptoms are accompanied by pneumonia which can be serious and potentially fatal.

It’s likely that we’ve not seen the end of this outbreak, and health officials are still working on confirming suspected cases. The disease can persist for up to a few weeks, so it’s still possible there are undiagnosed cases yet to be discovered.