The Maryland Transportation Authority shut down its Baltimore Harbor Tunnel cash toll booths this week after two employees were diagnosed with Legionnaires’ disease, raising a concern among some: Could drivers have caught it?
The Maryland Department of Health has taken samples, but no preliminary findings have been shared and it’s unclear whether either the toll booths or the administrative building — also shut down in the scare — were the source of the Legionella bacteria. The bacteria can cause Legionellosis disease, a form of pneumonia which results in flu-like symptoms, including headache, cough, fever, chills, shortness of breath, muscle aches and diarrhea.
But even if the Harbor Tunnel toll booths did contain the bacteria, most drivers had little chance of contracting Legionnaires’ while handing their $4 to a toll worker, said Tamara O’Connor, an assistant professor in the Department of Biological Chemistry at the Johns Hopkins School of Medicine who has studied the bacteria’s development.
The Legionella bacteria, which lives in water, is usually contracted through contaminated water vapor in the air, not transmitted person-to-person, O’Connor said. People with healthy immune systems are generally able to fight off the bacteria without becoming ill, and the risk of exposure in the few moments it takes to stop and roll down the window at the toll booth is “probably minimal,” she said.
The elderly and those on immunosuppressants are most at risk of catching the disease, O’Connor said.
“The vast majority of people probably have nothing to worry about,” she said. “It’s a very limited population who are susceptible. ... If [you] start to feel sick, obviously you want to go see your doctor."
The MdTA has not identified the infected employees, and it referred questions about the situation to the Department of Health.
The source of the exposure has not yet been determined, and environmental testing for Legionella takes 10-14 days, according to Kimberly Lang, a health department spokeswoman.
Lang declined to say when, other than “recently,” the infections were identified and declined to provide an update on the infected state employees’ conditions, citing health confidentiality laws.
The transportation authority, which operates and maintains the state’s tolled bridges, tunnels and express toll lanes, has 172 full-time toll workers and supervisors and 63 contract workers.
A staff of 60 toll collectors, including contractors, normally works at the location, according to MdTA spokesman John Sales. The two infected workers were on a shift rotating between the booths and the building, “depending on assignment,” Sales said.
Legionella is relatively common. The bacteria is present in about a third of all potable water systems, O’Connor said.
When the bacteria causes illness, it generally comes in two forms: Legionnaires’ disease, which is treated by antibiotics, and a less-serious illness known as Pontiac fever, which is a “self-resolving, flu-like illness” that doesn’t require medication, she said.
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Infections most often occur when stagnant, contaminated water in cooling towers is converted to a mist, usually in air-conditioning units, and breathed, she said. An estimated 10,000-20,000 cases are reported per year in the U.S., she said.
“In the vast majority of cases, the water in the cooling tower that feeds the air conditioning is contaminated," O’Connor said.
In one indication this could have been the case at the Harbor Tunnel facilities, Sales confirmed Wednesday that the toll booths and nearby administrative building share a connected ventilation system.
If the ventilation system was the source, sitting for long periods of time in the cramped quarters of a toll booth with the air-conditioning blasting could have increased the toll collectors’ risk of infection, O’Connor said.
“The smaller an area, the more concentrated, so the higher your exposure is going to be,” O’Connor said.
Efforts on Wednesday to interview other toll workers and officials of the American Federation of State, County and Municipal Employees (AFSCME) Maryland, the union that represents the state workers, were unsuccessful.