Legionnaires Disease Outbreak Hong Kong update 5 March 2020

A Legionnaires Disease outbreak occurred in Hong Kong between 1st – 29th February 2020 with seventeen (17) patients diagnosed with no fatality reported by CHP.

The total number of cases reported by CHP is lower than 17 reported here because additional cases residing physically close (<1000m) to the Choi Hung MTR station and the Ngau Chi Wan market were excluded without any evidence of the distinction. Ngau Chi Wan market is a very popular wet market in the area, located on Clearwater Bay road, directly above the Choi Hung MTR station, it is high traffic area, used by people from the local estates, and the surrounding districts.

Popular Ngau Chi Wan Wet Market located above Choi Hung MTR station

In total 15 cases were declared by CHP, twelve (12) male, and three (3) female, most were elderly residing near Choi Hung / Ping Shek Estate in Hong Kong, most with underlying disease.

At least two Legionnaires disease cases (refer to the table below, cases 12 and 13) were not counted as part of this cluster, yet both people reside nearby, approx. 1000m from buildings with confirmed cases, and well within the typical range of infection caused by cooling towers.

Cases

click for larger image

CHP also reported on 4 March 2020, specimens from two (2) more patients, that is eight (8) in total, match the samples from two Choi Hung MTR station cooling towers taken before the towers were disinfected (by implication sampled before 4 Feb. 2020). What is unclear, the initial 6 patients were reported on 14-2-2020, and three weeks later the additional pair were reported.

The CHP report on 4 March 2020 [link] that the Choi Hung MTR cooling towers have been disinfected and the water sampling test result (not provided) was stated to be lower than the action level. However, the tower installation date is not reported therefore it is unclear which COP would be relevant. Assuming CHP refers to the latest 2016 COP, it can be deduced that the Legionella sampling result was <10 cfu/mL and the Heterotrophic Colony count (also known as the plate count) sampling was <100 000 cfu/mL.

The CHP report concludes with a total of 27 cases for 2020, compared with 105 cases in 2019, which equates to 25% of cases in 2019 cases.

UPDATE 6 March 2020

EMSD.gov.hkissued a press release for its regular Legionella testing [link] on 6 March 2020 with routine and epidemiological investigation information, for the latter, in the attachment annex 2 [link] titled Building locations of fresh water cooling towers detected with total legionella count at/above upper threshold (1,000 cfu/ml) with nuisance notices issued under PHMSO, the annex states that the MTR Choi Hung Station had a nuisance notice issued showing total 1700 cfu/ml Legionella count (above the action level).

EMSD press release dated 6-3-2020

Legionnaires Disease Outbreak Hong Kong update 1 March 2020

One late additional case was reported on 29-2-2020 involving a male admitted to hospital twice. Initially, the patient was admitted on 4 Feb. 2020, with pneumonia and discharged on 19 Feb. 2020, and then admitted again on 24 Feb. 2020 and Legionnaires Disease diagnosed. [CHP]

This additional case involved a male patient, aged 71 with underlying illnesses, who lives in Wong Shek House, Ping Shek Estate, Kwun Tong.

Given the initial onset date of this case and proximity, residing in Ping Shek Estate approx. 100m from the early cases involving Kam Shek House, this case must be classified as part of the Legionnaires’ Disease outbreak.

16 Feb 2020 Cooling Tower, Choi Hung, Hong Kong

Although MTR cleaning tower maintenance/inspection was witnessed on 16-2-2020, CHP has not released any further details.

Outbreak History

Legionnaires Disease Outbreak Hong Kong update 18 Feb 2020

Two (2) more Legionnaires Disease infections were reported on 18-2-2020, bringing the total number of Hong Kong cases to twenty two (22) and sixteen (16) of those reside near Choi Hung. The new cases report by CHP include:

  1. A male patient, aged 94 with underlying illness, who lives in Hung Shek House, Ping Shek Estate, Kwun Tong
  2. A female patient, aged 52 with underlying illness, who lives in Block 2, 22 Wing Ting Road, Ngau Chi Wan (Fire Service Married Quarters)
Legionnaires Disease Outbreak Location Map

The CHP report [link] lists fourteen (14) cases, attributing two cases (12 and 13) as residing in a different area, although physically close to the Choi Hung area, approx. 1000m from the buildings implicated in Choi Hung, Kowloon.

In earlier CHP reporting it’s noted that the Choi Hung MTR station has four cooling towers samples were taken before they were disinfected on 4 and 12 Feb 2020. And these match specimens from six (6) patients in the Choi Hung Area.

The novel coronavirus covid19 epidemic has increased awareness and heightened surveillance in Hong Kong. Since both diseases present with similar symptoms and both involve pneumonia, further Legionnaires Disease infections will be detected and diagnosed in the coming months.

legionella, legionnaires disease outbreak, Choi Hung, Ping Shek, cooling towers, Kowloon, pneumonia, Hong Kong

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