Early in the COVID-19 pandemic, case counts were used to measure the level of COVID-19 in communities. However, with the widespread use of at-home tests, which aren't reported to health departments, this measure became less reliable. Wastewater disease surveillance allows health departments to track illness levels, regardless of testing habits.
- Common tests (like swabs taken at the doctor's office) can only show a rise in cases as they are happening
- Viruses can be found in human waste days before symptoms appear, or even if symptoms never develop
- Wastewater data helps detect changes in respiratory illness levels before they are visible in reported cases
- Many other pathogens, like influenza and RSV, can be detected in wastewater
- Having early warning signs when cases are changing provides health agencies, clinics, and individuals a chance to prepare for a rise in respiratory illnesses
The Milwaukee Health Department collaborates with the Milwaukee Metropolitan Sewerage District (MMSD) to measure wastewater respiratory illness data from the greater Milwaukee area:
- MMSD collects wastewater samples from Jones Island and South Shore sewersheds twice a week
- The MHD lab tests the samples to measure the amount of respiratory illness present in Milwaukee community
- The data is tracked on the wastewater dashboard to monitor changes in respiratory illness levels over time
Wastewater data is useful in monitoring respiratory illness trends for planning emergency responses, but there are some limitations:
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It is not possible to use wastewater data to confirm cases of respiratory illness in individual people
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Wastewater surveillance is new, and the tests used to get this data can be different between states and health departments
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This data can only be used to look at respiratory illness trends in communities that are connected to the Jones Island and South Shore sewersheds
Influenza A and B are the two main types of flu that routinely spread in humans.
Influenza A viruses can infect both humans and animals, such as pigs and birds, while influenza B viruses only infect humans.
Influenza A viruses are more common and tend to be more aggressive and severe than influenza B viruses.