Delaware's Division of Public Health has declared a measles outbreak after confirming four cases among unvaccinated adult males in Kent County. The declaration meets the CDC's definition of three or more connected cases. Officials are conducting contact tracing and urging residents to verify their vaccination status. Measles is a highly contagious virus that can cause severe complications, but the two-dose MMR vaccine is 97% effective.
Measles outbreak declaration
▪The Delaware Division of Public Health confirmed four cases of measles as of July 22, 2026.
▪The U.S. Centers for Disease Control and Prevention (CDC) defines a measles outbreak as three or more cases connected by time and location.
▪The four confirmed measles cases are among unvaccinated adult males in Kent County, Delaware.
▪Measles was declared eliminated in the U.S. in 2000, but cases have resurged in recent years.
Contact tracing procedures
▪People who suspect they have measles are advised to isolate and call a healthcare provider before visiting a facility.
▪The Delaware Division of Public Health is conducting contact tracing to identify people exposed to the measles virus.
▪The Delaware Division of Public Health will notify exposed individuals to confirm their vaccination status and recommend treatment if necessary.
High-risk populations
▪Measles can have life-threatening health complications, particularly in children under 5 years old.
▪Unvaccinated people, pregnant individuals, the immunocompromised, and infants are at the highest risk for severe measles complications.
MMR vaccine efficacy
▪Two doses of the MMR vaccine are 97% effective at preventing measles in people who are not severely immunocompromised.
▪The CDC recommends children receive their first MMR vaccine dose at 12-15 months and a second dose at 4-6 years.
▪A person is considered immune to measles if they were born before 1957, had a lab test confirm prior infection or immunity, or received two doses of a measles vaccine.
Vaccination access locations
▪Delaware residents can check their vaccination status through the DelVAX Public Portal.
▪Public health clinics in Delaware offer MMR vaccines for uninsured or underinsured individuals.
▪In Delaware, MMR vaccines are available at pharmacies, federally qualified health centers (FQHCs), and other healthcare providers.
Measles transmission methods
▪The measles virus can remain infectious in the air and on surfaces for up to two hours after an infected person has left the area.
▪An infected person is contagious from four days before their rash appears until four days after it develops.
▪The incubation period for measles is about 10 days from exposure to fever and about 14 days from exposure to rash.
▪Measles is a highly contagious virus that spreads through the air via infectious droplets when an infected person coughs, sneezes, or breathes.
▪Measles symptoms include high fever, cough, runny nose, and red/watery eyes, followed by a rash 3-5 days later.
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