Southwest District Health (SWDH) is notifying healthcare providers of probable measles exposure
involving middle and high school-aged children in our jurisdiction. Approximately 2,000 middle and
high school-aged children may have been exposed to probable measles cases. Although laboratory
confirmation is not available, the clinical presentation and exposure history of these cases are
consistent with measles. Among those exposed, approximately 5.5% (~110) are either unvaccinated
or under vaccinated.
Exposure dates include:
• January 9, 2026
• January 20, 2026
Notification letters have been sent to parents/guardians of students at the affected schools
outlining the exposure dates, incubation period (average 8 to 14 days but can be up to 21 days since
exposure) and recommended next steps.
Provider Action Requested
• Maintain a high index of suspicion for measles in patients presenting with fever and rash,
particularly those with cough, coryza, or conjunctivitis and/or a relevant exposure history.
• Measles is immediately reportable. Please report all suspected cases to SWDH promptly.
• Immediately isolate suspected cases using airborne precautions and evaluate patients in a
manner that minimizes exposure to others.
• Measles is infectious 4 days before to 4 days after rash onset, with day of rash onset
counted as day ‘zero’.
• Offer testing if measles is suspected. Testing for all suspect measles cases should ideally
include both serologic testing and RT-PCR to optimize sensitivity and specificity of testing,
but if that is not feasible, a swab alone is acceptable, especially during the early days of the
rash, or for people with pre-existing immunity. See “Laboratory Testing” in
https://www.cdc.gov/surv-manual/php/table-of-contents/chapter-7-measles.htmlTesting Guidance
SWDH can assist with measles testing coordination.
• The Idaho Bureau of Laboratories (IBL) performs measles PCR testing only.
• Measles IgM and IgG serologic testing should be performed through other commercial
laboratories.
• Please contact SWDH to coordinate sample shipments to IBL.
Post-Exposure Prophylaxis (PEP) Recommendations
Individuals exposed to measles who cannot readily demonstrate presumptive evidence of immunity
should be offered post-exposure prophylaxis (PEP).
There are two types of PEP for measles. To potentially prevent disease or modify the clinical course
in susceptible individuals, administer one of the following:
• MMR vaccine, if administered within 72 hours of initial measles exposure
• Immunoglobulin (IG), if administered within 6 days of exposure. The recommended dose for
intramuscular immunoglobulin (IMIG) is 0.5 mL/kg, regardless of the contact’s immune
status.
o IG is recommended for pregnant women without presumptive evidence of
immunity, immunocompromised people (regardless of immune status) and infants
13307 Miami Lane, Caldwell, ID 83607 208-455-5300 208-454-7722 SWDH.org
less than 6 months of age. Infants aged 6-11 months can receive MMR vaccination
for PEP within 3 days of exposure.
o MMR vaccine and IG should not be administered simultaneously, as this practice
invalidates the vaccine.
SWDH is available to support vaccination and testing efforts. Individuals can schedule an
appointment with us by calling 208-455-5300.
Presumptive evidence of immunity to measles includes any of the following:
• Written documentation of adequate measles-containing vaccination
• Laboratory evidence of immunity
• Laboratory confirmation of prior measles disease
• Birth before 1957
If you have questions, need assistance with testing or PEP, or would like to discuss a suspected case,
please contact Southwest District Health Epidemiology at 208-455-5442.