Measles Wastewater Detection in Ada County

Central District Health (CDH) is notifying healthcare providers of an isolated detection of measles virus RNA in wastewater collected on April 22, 2026, from a wastewater facility serving Boise. At this time, CDH has not been made aware of any suspected or confirmed measles cases among residents of Ada County.

Detection of measles virus RNA in wastewater indicates that one or more infected individuals may have been present in the wastewater catchment area, even if they have not sought medical care. Wastewater signals can precede clinical detection and serve as an early warning indicator. Clinicians should heighten their suspicion of measles in patients presenting with fever, rash, cough, coryza, or conjunctivitis, particularly if they are unvaccinated.

Requested Actions 

• Report suspected measles immediately at the time of clinical suspicion to your local public health district (do not wait for lab confirmation).
• Consider measles in patients with compatible symptoms (fever and rash, with cough/coryza/conjunctivitis).
• Collect and ship specimens correctly for measles testing (PCR ± serology).
• Implement airborne precautions immediately for suspected cases.
• Review MMR vaccination status and be prepared to counsel families on the importance of testing and quarantine or isolation, as indicated.
• Encourage MMR vaccination for patients who are not up to date as part of standard preventive care, given evidence of measles virus circulation in the community.

Clinical Presentation of Measles

• Measles (rubeola) is a highly contagious viral illness.
• Prodrome (2–4 days): high fever (≥103°F), cough, coryza, conjunctivitis (“3 C’s”).
• Koplik spots: bluish-white lesions on the buccal mucosa, appearing 1–2 days before rash onset.
• Rash: maculopapular, begins at the face/hairline and spreads downward to trunk and extremities; lasts several days.
• Infectious period: 4 days before through 4 days after rash onset.
• Complications: otitis media, pneumonia, encephalitis; highest risk among children <5 years, pregnant people, and immunocompromised persons.

Clinicians should consider measles in any patient with clinically compatible symptoms, especially if they are unvaccinated, report an exposure to measles, or have traveled internationally or to an area in the U.S. with a current measles outbreak.

Testing and Specimen Collection

Do not delay specimen collection. Obtain specimens at the first evaluation of a suspected case.

Preferred Specimens

• Throat or nasopharyngeal swab for RT-PCR (preferred early in illness).
• Serum for measles IgM (note: specimens collected <72 hours from rash onset may be falsely negative).

Collection & Shipping Instructions

• Use synthetic-tipped swabs (polyester/nylon) with plastic or metal shafts only.
• Place swab(s) in 1–3 mL Viral/Universal Transport Medium (VTM/UTM).
• Transport specimens refrigerated (2–8°C) in a cooler with cold packs.
• Refrigerated (2–8°C): deliver within 72 hours of collection.
• Frozen (≤ -20°C): if >72 hours to delivery, freeze and ship on dry ice (do not allow thawing).
• Ship as Category B diagnostic specimens.

Important Testing Notes:

• The Idaho Bureau of Laboratories (IBL) provides measles RT-PCR.
• If serology testing is desired, specimens should be referred to a commercial reference laboratory.
• The test is specific for wild-type measles and does not detect the vaccine strain.
• Providers should contact public health before submitting specimens to IBL. If after-hours testing is needed for highly suspect cases, providers must coordinate testing with public health and IBL before submitting specimens.

 Reporting 

• Business hours: Central District Health at 208-327-8625
• After hours/weekends: State Communications Center 1-800-632-8000 (request public health epidemiology)
• Report at the time of initial clinical suspicion.

 Early reporting allows public health to rapidly assess exposures, provide post‑exposure guidance, and limit unnecessary quarantine or school exclusion.

 What to Say to Families about Measles Testing

 Provider encouragement of testing is essential for effective outbreak prevention and an accurate public health response. CDH can facilitate or directly provide measles testing at no cost to the family to help prevent community spread.

 Suggested language when discussing testing with families:

• Measles is extremely contagious. Testing helps public health identify where the virus is so we can protect infants, pregnant people, and those with weakened immune systems.
• Fever and rash have many possible causes. A lab test confirms whether this is truly measles or something else that may need different follow‑
• There is no cost barrier. Central District Health can help arrange measles testing at no cost for the family.
• Testing supports families. A simple test is not a mandate — it provides information to help families understand what their child is experiencing and make informed care decisions.
• Confirmed measles results in lifelong immunity. With lab confirmation, future exposures usually do not require quarantine, repeat testing, or school or activity exclusion.

Resources:

• U.S. Centers for Disease Control and Prevention Clinical Overview of Measles: https://www.cdc.gov/measles/hcp/clinical-overview/index.html
• U.S. Centers for Disease Control and Prevention Measles Toolkit: https://www.cdc.gov/measles/php/toolkit/index.html
• Idaho Bureau of Laboratories: https://healthandwelfare.idaho.gov/providers/idaho-laboratories-and-testing/idaho-bureau-laboratories
• Idaho Public Health Districts: https://healthandwelfare.idaho.gov/health-wellness/community-health/public-health-districts

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