User:K8-25/1993 Milwaukee Cryptosporidiosis outbreak

During the spring of 1993, the largest recorded waterborne disease outbreak in the U.S. of Cryptosporidium occurred in Milwaukee, Wisconsin. From the investigation, it is suspected that The Howard Avenue Water Purification Plant, only one of two water treatment plants in Milwaukee, was contaminated. Approximately 403,000 residents were affected resulting in illness and hospitalization. Immediate repairs were made to the treatment facilities along with continued infrastructure upgrades during the 25 years since the outbreak. The city of Milwaukee has spent upwards to $510 million dollars in repairs, upgrades, and outreach to citizens.

Epidemiology

On April 5, 1993, Milwaukee Health Department received increased reports of gastrointestinal (GI) illness at their local hospitals and calls of complaints related to reduced water-quality aesthetic. Water aesthetic includes taste, color, odor, hardness/softness, and turbidity are considered a secondary standard under the EPA National Primary Drinking Water Regulations (NPDWR). Although these drinking aesthetics are under the EPA NPDWR, they are not federally enforced but standard regulations that states may chose to adopt and enforce themselves. Public health officials suspected recent illness to be due to water consumption. To verify suspicions, both the water treatment plants complied data of 30 days prior to the incident. The only findings were that turbidity were slightly increased but still below federally recommended levels. At the same time, hospitals did not routinely screen for cryptosporidium but because patients were all experiences similar symptoms hospitals were asked to test for cryptosporidium. Cryptosporidium is a chlorine resistant enteric pathogen that causes gastrointestinal illness such as diarrhea. Independent tests were run through the Milwaukee Public Health Laboratory (MHDL), to test stool samples for cryptosporidium. On April 7th, two days after initial reports, the Mayor of Milwaukee issued a ten-day advisory for residents to boil their drinking water. The process of boiling water is effective is killing potential pathogens however, this method cannot be used on a wide-scale as it is not as effective as water treatment plants and in some instances can be harmful. Furthermore, boiling water is only useful for drinking water. This means that people can still come into contact with harmful pathogens through their through showers, washing machines, and sinks.

Burden of disease

The economic burden of this outbreak heavily impacted residents and workers in Milwaukee. To understand this impact, the CDC partnered with the Milwaukee and Madison health department to conduct a four-month cost analysis breakdown through the use of phone surveys, household estimate, and hospital cost estimates. To assess the finical burden to residents, they sorted patients based on the degree of medical attention received. Mild cases were described as not receiving medical care during illness, moderate were described as receiving medical care but not hospitalis, and severe cases were those who were hospitalized. The results of their studied found that for for mild cases average cost of illness per person was $116, moderate was an average of $475, and severe averaged $7,800. Fees included transportation, screening, laboratory tests, number of days in hospital, and productivity loss of an average worker.

Response

In response to the incident,

Nationwide improvement of water-quality standards
- EPA Surface Water Drinking Rules were amended
City of Milwaukee started following the USEPA Interim Surface Water Drinking Rules
Hospital screening were adjusted to accurately represent cryptosporidiosis symptoms
- Additionally, outpatient screen was reviewed for better follow-up.
Local partnership with Milwaukee Wastewater treatment plants and health department to ensure communication and response to public. The collaboration is called the Interagency Clean Water Advisory Council (IACWAC).
Renovation of wastewater treatment plant in 1994 to uphold to new EPA and Wisconsin DNR standards.
Approximately $415 million dollars were investment to improve the city's water infrastructure.