Monday, July 16, 2018

Legionella Cases Rising


Forty-two summers ago the world was anxiously waiting to see whether a recently discovered novel H1N1 flu virus - detected among soldiers the previous winter at Fort Dix, N.J. - would return as a pandemic.  
As a young paramedic, I played a very minor role in our county health department's response, which you can read about in Deja Flu, All Over Again.
Although the dreaded swine flu pandemic never manifested, the summer of 1976 is notable for the outbreak of a - then unidentified illness - among attendees of an American Legion bicentennial celebration held at the Bellevue-Stratford Hotel in Philadelphia.

Within days of returning home from the convention, more than 180 people would fall ill with (often) severe flu-like symptoms, and at least 29 died.  Notified by a doctor who saw multiple patients fall ill after attending the convention, the CDC launched an investigation. 
Pandemic influenza was ruled out fairly quickly, and four months later a CDC lab would identify the culprit as an aquatic gram-negative bacterium - subsequently dubbed Legionella pneumophila - which could cause mild to severe pneumonia.
Legionella wasn't new of course, just finally isolated and identified. Its discovery led to retrospective identification of previous outbreaks, including an earlier outbreak at the same Philadelphia hotel (see The Lancet 1974 outbreak of Legionnaires' Disease diagnosed in 1977).
A milder version of Legionnaires' Disease, known as Pontiac Fever, was also identified following the 1976 Legionnaire's outbreak. 
We now know that the Legionella bacteria grow readily in older, or poorly maintained, (usually warm) fresh water sources and can be aerosolized by air conditioners and cooling systems, hot tubs, fountains, and even shower heads.

 Although many are able to fight off the infection, and remain asymptomatic or only mildly ill, those who are over 50, are former or current smokers, or who have a weakened immune system are the most likely to develop pneumonia. 
And although the cause isn't known, as the chart at the top of this blog indicates, the number of identified cases has quadrupled since the year 2000.  While a lot of this may be due to better testing and surveillance, there may be other factors at work as well. 
You may recall that during the summer and fall of 2015, NYC saw no fewer than 3 outbreaks of this bacterial pneumonia - including one that resulted in 138 cases and 16 deaths - all linked to a single cooling tower in the South Bronx.
The CDC estimates that between 8,000 and 18,000 Americans are hospitalized with Legionnaire's Disease each year.  As many people who contract this type of bacterial infection experience only minor symptoms, this is likely an under count of the total affected.

Last week the State of Michigan published the following press release on a recent spike in local cases.
CONTACT: Lynn Sutfin, 517-241-2112

LANSING, Mich. – The Michigan Department of Health and Human Services (MDHHS) is coordinating with local health departments across the state to investigate cases of legionellosis this summer. To date in 2018, there have been 135 confirmed cases of legionellosis reported in 33 counties compared to 107 confirmed cases during the same timeframe in 2017. 

Confirmed cases include 24 in the City of Detroit, 19 in Macomb County, 16 in Oakland County, 11 in Wayne County and 10 in Genesee County. Twenty-four cases have been confirmed statewide since July 1, and another 13 cases are pending confirmation.

This increase corresponds with national increases in legionellosis. Legionellosis is most common in the summer and early fall when warming, stagnant waters present the best environment for bacterial growth in water systems.

MDHHS and local health departments are working to inform healthcare providers of the increase in cases and share information regarding testing and treatment. Legionellosis is a respiratory infection caused by Legionella bacteria. Legionnaires’ disease is an infection with symptoms that include fever, cough and pneumonia. A milder form of legionellosis, Pontiac fever, is an influenza-like illness without pneumonia that resolves on its own. 

Legionella bacteria are found naturally in fresh water lakes and streams but can also be found in man-made water systems. Potable water systems, cooling towers, whirlpool spas and decorative fountains offer common environments for bacterial growth and transmission if they are not cleaned and maintained properly. Warm water, stagnation and low disinfectant levels are conditions that support growth in these water systems.

Transmission to people occurs when mist or vapor containing the bacteria is inhaled. Legionellosis does not spread person to person. Risk factors for exposure to Legionella bacteria include:
  • Recent travel with an overnight stay.
  • Recent stay in a healthcare facility.
  • Exposure to hot tubs.
  • Exposure to settings where the plumbing has had recent repairs or maintenance work.
Most healthy individuals do not become infected after exposure to Legionella. Individuals at a higher risk of getting sick include the following:
  • People over age 50.
  • Current or former smokers.
  • People with chronic lung disease.
  • People with weakened immune systems from diseases, such as cancer, diabetes or liver or kidney failure.
  • People who take immunosuppressant drugs.
Individuals with any concerns about Legionnaires’ disease or exposure to the Legionella bacteria should talk to their healthcare provider. MDHHS and local health departments will continue to monitor cases and provide updates to the public. More information on Legionella and Legionnaires’ disease can be found on the Centers for Disease Control and Prevention website.

Despite the statement above, saying that `Legionellosis does not spread person to person', in 2016 in NEJM: Probable Person-to-Person Transmission Of Legionnaires’ Disease, we saw an epidemiological investigation following the 2014 outbreak in Portugal that strongly suggests that - while very rare - it is possible.

The CDC's Fast Facts on Legionella now states:
In general, people do not spread Legionnaires’ disease to other people. However, this may be possible under rare circumstances. 
Legionella is just one of many causes of Community Acquired Pneumonia (CAP), which combined cause roughly 1 million hospitalizations, and about 50,000 deaths, each year in the United States. 

Somewhat surprisingly, the causative agent in more than half of all CAP cases is never identified, although viral infections appear to out-number bacterial infections by roughly 2:1.

In 2010, the CDC began their EPIC Study (Etiology Of Pneumonia In the Community) – which they describe as a:
. . .  prospective, multicenter, population-based, active surveillance study; systematic enrollment and comprehensive diagnostic methods were used. The main objective of the EPIC study was to determine the burden of pneumonia hospitalizations in U.S. children and adults as well as to identify viruses and bacteria associated with these hospitalizations.
We looked at the results in 2015's The CDC’s EPIC CA-Pneumonia Study, but briefly they found:
  • one or more viruses in 530 (23%) cases
  • bacteria in 247 (11%) cases
  • bacterial and viral pathogens in 59 (3%) cases
  • and a fungal or mycobacterial pathogen in 17 (1%) of cases
The most commonly detected pathogens were:
  • Human rhinovirus (in 9% of patients)
  • Influenza virus (in 6%)
  • and Streptococcus pneumoniae (in 5%).

Whether the increase in Legionella the past twenty years is a product of better lab testing, an older society more prone to infection, or aging infrastructures which are more likely to grow and aerosolize the bacteria, is up for for debate.
In all likelihood, all play some part.
There are things you can do to help protect yourself, however.  You should talk to your doctor about pneumococcal vaccines, as they can significantly reduce your risk of developing pneumonia from the covered strains. (note: Legionella isn't among those strains covered by the vaccine).

Beyond vaccines, the CDC recommends:

Protect Your Health with These Healthy Living Practices

Try to stay away from sick people. If you are sick, stay away from others as much as possible to keep from getting them sick. You can also help prevent respiratory infections by:
  • Washing your hands regularly
  • Cleaning surfaces that are touched a lot
  • Coughing or sneezing into a tissue or into your elbow or sleeve
  • Limiting contact with cigarette smoke
  • Managing and preventing conditions like diabetes

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