Staggering 84 percent of measles cases in major Chicago outbreak linked to Venezuelan migrants, CDC report shows

Some 84 percent of deadly measles cases in a recent major outbreak at a migrant center in Chicago are linked to Venezuelan immigrants, a new CDC report shows.

New information reveals that the spate of 57 cases at the Pilsen migrant shelter can be traced back to a one year-old boy who had only received one of the two vital vaccines.

The majority of the cases — 72 percent — were among unvaccinated people, the CDC said.

The report cites overcrowding at the center for the rampant spread, with 500 people said to be crammed into a single room. 

Chicago is at the epicenter of the measles outbreak in the US, with 64 cases recorded so far

Migrants pictured at a makeshift shelter in Chicago's Pilsen neighborhood, where many are being moved to. There has been an outbreak of measles and tuberculosis linked to the shelter

The first patient had arrived in the US less than five months before he became ill. He had received one dose of the MMR vaccine five weeks prior to his rash. 

He had no recent travel history or known exposure to measles, and was taken to the hospital on February 27.

The Chicago Department of Public Health was notified of the case a few days later, and organized a vaccination event for the residents and staff members of the shelter the next day.

Because of the highly infectious nature of measles, they considered anyone who had been inside the shelter between February 22-27 - the boy's infectious period - to have been exposed to measles.

Between February 26 and May 13, there were 57 confirmed cases linked to the shelter, including 52 among migrants staying at the shelter and three among staff members.

The median age of infected migrants was three years old, and most were originally from Venezuela. Four were from Peru, two from Ecuador, one from Chile and a further one whose origin country was not known.

Since August 2022, roughly 41,000 migrants have arrived in Chicago, Illinois from the US southern border.

Of those, 88 percent are from Venezuela - a country that has seen a recent decline in routine child vaccination coverage, including the measles vaccine.

The surge in migrants comes as Chicago continues to pride itself as a 'sanctuary city', or a location where people can ask for aid from city services without revealing their immigration status. 

Officials also do not ask residents about whether they are legally entitled to be in the US. 

Some 30 of the 57 cases at the Pilsen center were in women, and 27 were in men. Most of the patients were between six months old and four years old, followed by 20-49 years old.

Measles typically begins with cold-like symptoms, before causing a rash made up of small red spots, some of which can feel slightly raised

The Pilsen migrant shelter is the largest in Chicago, and was hosting around 2,100 people in late February, with more than 500 people residing in some of the rooms.

Migrants themselves have said illnesses are rampant in shelters because of overcrowding and unsanitary conditions. 

Around 130 Americans have been struck with measles this year, amid warnings that falling vaccination rates and surging immigration is leaving America's children more vulnerable to the disease than ever before. 

The CDC says infants should receive their first dose of the measles vaccine at the age of 12 to 15 months, and their second dose between the ages of four to six years. 

Studies show the first dose is 93 percent effective against the virus while the second is 97 percent effective.

Vaccinated people can still get sick, doctors say, but they have a much milder infection because they already have immunity.

Dr Thomas Moore, an infectious disease expert, previously told DailyMail.com: 'If you want to create a public health crisis, put people in over-crowded spaces.'

Overcrowding, unsanitary conditions and limited accessibility to vaccines in migrants' native countries can all cause and exacerbate outbreaks in shelters, he said.

Measles was declared eliminated in the US in 2000, which means the disease is no longer constantly present in the country.

America's measles elimination status was threatened in 2019 due to two prolonged outbreaks among under vaccinated communities in New York.

According to the CDC, MMR vaccine coverage dropped a further two percent between the 2019-2021 school year to the 2022-2023 school year, which means that roughly a quarter of a million kindergartens are at risk of measles infection across the US.

The 93.1 percent rate during the 2022–23 school year is lower than the 95 percent rate in the 2019-2020 school year, leaving measles coverage below the national target of 95 percent for the third year running.