Kane County Confirms Measles Case as US Infections Hit 35-Year High

The Kane County Health Department has confirmed a measles case in a local resident and is now working to identify anyone who may have been exposed to the highly contagious virus. Officials say the disease spreads through airborne transmission when an infected person coughs or sneezes, and can linger in an enclosed room for up to two hours after that person has left. The department is coordinating with the Illinois Department of Public Health to investigate the case.

Michael Isaacson, spokesperson for the Kane County Health Department, said the agency's priority is identifying potentially exposed people and providing timely guidance, as reported by FOX 32 Chicago. Isaacson also urged residents to keep themselves and their children up to date on MMR vaccines, calling the shot very effective. Health officials warn that measles exposure can infect up to 90% of unprotected close contacts, according to the CDC, and that additional cases could surface in the coming days based on who was exposed.

The Kane County diagnosis lands amid a national surge that has pushed 2026 measles cases to their highest level in 35 years. Nationwide case counts reached 2,777 as of August 21, according to CIDRAP, already surpassing the 2,289 cases recorded across all of 2025 and marking the highest annual total since 1991. Weekly case additions recently doubled to 211 new infections, driven largely by outbreaks in Pennsylvania and Ohio, per the same outlet.

Who Is Most at Risk

Of the U.S. cases reported through August 21, 94% occurred in people who were unvaccinated or had unknown vaccination status, and children and teenagers accounted for 66% of infections, CIDRAP reports. Children aged 5 and under made up 19% of all 2026 cases. Higher-risk groups for severe complications include children younger than 5, adults older than 20, pregnant women, and people with weakened immune systems, according to information cited by FOX 32 Chicago.

The stakes of infection go beyond a rash. Measles hospitalizes one out of every four infected people in the United States and can kill up to two out of every 1,000 infected children, per the same report. Severe complications can include pneumonia, brain damage from swelling, and deafness. Fevers can exceed 104 degrees Fahrenheit, and the rash itself typically starts at the hairline before spreading to the arms and legs three to five days after symptoms begin — symptoms that generally emerge 10 to 21 days after infection.

A Year of Rising Case Counts Nationally and in Illinois

In 2025, the U.S. recorded three measles deaths, matching the total number of measles fatalities nationwide across the entire 24-year span from 2001 through 2024, according to the Illinois Department of Public Health. Two of those three 2025 deaths were young children. The U.S. reported more measles cases, outbreaks, affected states, and deaths in 2025 than in any year since 1992, according to KFF, even though the country had declared measles eliminated back in 2000, per the CDC.

Illinois had already logged four confirmed measles cases statewide earlier in 2026 before the Kane County diagnosis, following 14 cases in 2025 and 67 in 2024, the state health department notes. The state's first 2026 case involved an adult traveler in the Metro East region in February. Illinois's largest outbreak since 1990 struck between March and May 2024, when 67 confirmed cases were mostly concentrated at a Pilsen migrant shelter in Chicago before spreading to suburban Cook, DuPage, Lake, and Will counties — a response that included a mass vaccination blitz verifying records for more than 1,600 shelter residents within days.

Cook County has already dealt with high-traffic exposure sites this year. Health officials there issued public warnings in late March after an infected individual visited O'Hare International Airport's Terminal 5, retail stores in Niles, and an immediate care clinic in Mount Prospect while contagious, according to the Cook County Department of Public Health, a case Hoodline previously reported. State health officials did manage to fully contain an earlier cluster: in July 2025, they declared an end to an eight-case Southern Illinois measles outbreak after two full 21-day incubation periods passed without new cases.

Vaccination Gaps Behind the Surge

National kindergarten and childhood measles vaccination coverage has fallen to 92.5%, below the 95% threshold required to prevent sustained transmission, according to figures cited by FOX 32 Chicago. Illinois kindergartners posted a vaccination rate of about 93% during the 2025-2026 school year, still short of that herd-immunity benchmark. The state's Illinois Department of Public Health has responded by building an interactive Measles Outbreak Simulator Dashboard, which uses state education data and a compartmental epidemiological model to help officials and parents evaluate individual school outbreak risks.

Under Illinois State Board of Education nurse guidelines, unvaccinated students without documented proof of immunity who are exposed to measles must be excluded from school and quarantined for 21 days following their last exposure. Post-exposure vaccination within 72 hours can exempt students from that quarantine. The state also maintains Vax Verify, an online database that tracks vaccine records.

The measles vaccine remains highly effective: the CDC puts effectiveness at 93% after one dose and 97% after two doses. People vaccinated after 1989 have likely received two doses, while those vaccinated between 1957 and 1989 may benefit from a booster. People born before 1957 generally do not need a booster because they were likely exposed to the disease naturally. Some vaccines administered between 1963 and 1967 were inactive, a detail relevant to older adults checking their immunization history. Canada, for comparison, lost its measles elimination status in late 2025, according to the Associated Press.

What Kane County Residents Should Do

The Kane County Health Department is now informing people who may have been exposed and is monitoring for potential additional cases. Anyone who may have been exposed and needs to see a healthcare provider is asked to call ahead so precautions can be taken before arrival. The department provides childhood immunizations to Medicaid-plan, uninsured, or underinsured children up to their 19th birthday, and also offers adult vaccines to uninsured or underinsured adults, alongside general education about measles and preventive measures.

Residents with questions or concerns can reach the Kane County Health Department at 630-208-3801. The case adds to a string of measles alerts across the Chicago area this year, including exposure warnings tied to O'Hare's Terminal 5 and a Zion school district's push to close vaccination gaps. Whether the Kane County case stems from international travel or domestic transmission, and whether contact tracing will reveal additional public exposure sites, remains unclear as the investigation continues.