Outbreak Analysis

chart Finally, only one new case is reported during the first week of December. It seems that public education and other efforts to control the spread of Giardiasis are working.

The Dunnit LBOH must still work to determine what caused and sustained the outbreak.

Based on their findings, the LBOH in Dunnit will make determinations about how to proceed with policy or enforcement actions. The country club pool and food establishments are regulated by the LBOH in Dunnit and require annual permits and routine inspections.

In collaboration with MDPH and CDC, the Dunnit LBOH has now found out this information about the 97 laboratory confirmed cases:

  • 72% were members (including children) of the county club
  • 17% were guests of the country club
  • 11% had no link to the country club

The CDC wants to gather more information to better understand the country club link. With the country club's cooperation, the EIS officer develops a questionnaire and sends it to all country club members.

The questionnaire asks about:

  1. Symptoms, length of symptoms, and medical attention
  2. Exposure to country club pools, food, and other community pools
  3. Use of diaper changing stations at country club pool area restrooms
  4. History of other possible exposures (i.e., camping or hiking)
  5. Relatedness to other cases (i.e., playgroups or babysitters)

30 primary, 105 secondary, 14 unknown cases Of the 498 members that received the questionnaire, 175 completed it. Results indicate that most of the cases were children (median age 6 years for primary and 5 years for secondary).

Of the 149 cases identified by the survey (not laboratory analysis):

  • 30 were primary
  • 105 were secondary
  • 14 were unknown

A primary case is defined as a case whose illness onset was between June 2 and October 5, and who had no contact with an ill individual during their shedding period. A secondary case is defined as a case whose illness onset was on or after October 5, or who had an illness onset within 60 days of contact with another case.

The country club pools were closed on September 5, so, given the incubation period of Giardia (up to 30 days), it was estimated that a case could be linked to a pool exposure and become symptomatic no later than October 5.

Statistical analysis determined an increased risk for those who swam in the wading pool, but no significant risk for those who used the swimming pool.

 

The research article about the actual case can be found in the Additional Resources (last page of this training).

 

Policy Decisions

Think about actions the LBOH in Dunnit should take, especially for the swimming and wading pools (both of which will require a permit from the LBOH next summer).

In the actual case, there had been an unreported fecal accident in the swimming pool in mid-July that was discovered during the case investigations. The Certified Pool Operator (CPO) was overruled by the club manager and forced to re-open the swimming pool without following the MDPH policy to response to fecal incidents.

The DBOH took a number of actions. They scheduled a hearing with the country club and required them to:

  1. Hire an outside investigator regarding the handling of the fecal accident, and to share the report with them by a certain date.
  2. Hire a pool maintenance company to review and/or develop pool maintenance policies, and to conduct staff training.
  3. Formally adopt the MDPH policy to respond to fecal incidents.
  4. Have a CPO on the premises whenever the pools were open.
  5. Develop a corrective action plan for pool operations that would be reviewed by the Health Director and approved by the Dunnit LBOH at a later meeting. The plan had to include immediate notification to the Dunnit LBOH of any fecal incident, ensure the CPO was the decision maker to re-open the pool, and empower the lifeguards to enforce the state regulations.
  6. Conduct a water quality test for bacteria and parasites prior to opening for the next season.
  7. Monitor handwashing and diaper-changing facilities.
  8. Improve signage and record keeping.

The Dunnit LBOH was satisfied with the country club's response, and the pools were opened the next summer with no further cases of disease. The LBOH did realize they needed to improve risk communication (as they did not have a plan/protocol in place at the time of the outbreak), and sent staff to appropriate training so the LBOH could adopt a written communication plan.