Marshalltown Legionella outbreak over after 28 days with no new cases

MARSHALLTOWN — The Legionnaires’ disease outbreak that sickened 74 people and led to two deaths in Marshalltown in August and September has been declared over after more than a month without any new cases.

Legionnaires’ disease is caused by Legionella bacteria, which thrive in warm water and typically spread when a person inhales aerosolized water droplets.

State and local public health officials said they believed the source of the Marshalltown outbreak was a cooling tower. Early in the outbreak, they said all of the cases had been in residents who live in the north central part of the city.

Marshall County Public Health Director Sydney Grewell provided a final update on the outbreak to the Marshall County Board of Supervisors Wednesday, noting that all of the businesses with cooling towers in the suspected area of the outbreak have completed additional remediation processes.

The last case of Legionnaires’ disease was reported on Sept. 25 — about six weeks ago. The outbreak was considered concluded on Oct. 23, when no new cases were reported for 28 days.

“The incident command structure has closed at the state level as well as at the local level,” Grewell said.

Health officials tested each of the 12 suspected cooling towers multiple times in an attempt to find the matching sequence or fingerprint, and one business center did test positive for Legionella pneumophila serogroup 1 (Lp1), the bacteria that causes Legionnaires’ disease, but it did not match the patient who was infected.

“So we still don’t have a smoking gun, and we may never find the smoking gun, unfortunately. But the fact that we found Legionella at all means that we’ve been on the right track this entire time,” she said.

Grewell said the remediation process for businesses included shutting down the towers and performing extensive cleaning, which is neither easy nor cheap.

“Each of the 12 businesses with cooling towers started additional disinfection work or online remediation early to mid-September. Ten of those businesses have completed full offline remediation (which is completing an extensive disinfection process). The remaining two are shut down for the season and will complete their offline remediation prior to going back online next season,” she said.

Moving forward, any Legionella case reported to Grewell and the state will not be considered part of the outbreak and will instead be considered one of the 30 to 70 cases typically reported every year.

“I just want to say thank you to all of the local partners, the business centers, community partners, state, federal, Board of Supervisors, Board of Health, everybody that was involved in this outbreak response, and we will continue to press forward,” she said.

Grewell has fielded questions about potential regulation of cooling towers going forward, and she told the board it would likely need to be handled at a local level by either a city or county ordinance. Supervisor Jarret Heil asked if the identity of the business center that did test positive for Legionella would be made public.

She said that the information would not be made public as the business’ privacy is protected under the Iowa Code section 139A for communicable disease because it is not an ongoing threat, and the problem was mitigated. Heil followed up with a question about whether it would have been different if a definitive match had been determined.

“That is something I am not fully sure of, but I still believe that they might not have shared it because, again, they took care of the process,” Grewell said. “If the business center would have just not done anything and not cooperated, then maybe there would’ve been some different actions taken. But again, all business centers cooperated, which was very good on our part. Some of them may have taken a little longer. Some of them may have taken a little longer for us to get in there and provide their information, but all of them did do the processes that we were asking them to, which again, a lot of them were big financial undertakings for these places. (It’s) not cheap to clean cooling towers.”

Supervisor Kevin Goodman called the situation “a difficult subject” and wondered why the outbreak happened specifically in Marshalltown. Grewell replied that it was hard to know because cooling towers are located all over the state and the country. She said it could have been negligence by the business owner through improper water management processes.

“I think this experience has opened up the eyes of everybody — not only business owners but people — to make sure that they have water management processes, and they are handling them appropriately,” Grewell said.

Other local public health agencies across Iowa are asking the same questions, she added, and Legionella can develop from other sources such as CPAP and BiPAP machines, showers and faucets.

“I think this was a learning curve for many of us. I had never even heard what this was. I had no idea what Legionella was. I had no reason to know what it was before this, so I learned a lot about it,” Heil said. “At times, the public’s wanting to know information right away in real time, and we do the best we can on that. And I thought you did that as well. At the same time, there are laws we’ve got to follow on making sure that personnel information and particular information is protected. You did that well, and for us to have a close to this now is a good chapter to have closed. We look forward to not having to work on these things again, but you’re certainly prepared to do so if we do.”