(NewsNation) — A Chicago alderman who says he has tried to raise the alarm about migrant health issues says Mayor Brandon Johnson has covered up the matter despite knowing about existing measles and tuberculosis cases that have existed inside city-run shelters for months.

Ald. Raymond Lopez told NewsNation on Thursday that Johnson’s administration has “tried to cover this up from the jump,” not wanting to recognize the public health crisis that was forming in Chicago.

“This is not new,” said Lopez, who represents Chicago’s 15th Ward. “This has been going on for a long time, and it has become too much to hide.”

The Chicago Department of Public Health only confirmed “a small number” of tuberculosis (TB) cases in a few shelters Wednesday.

Lopez posted images on social media of shelter incident tickets filed by the Chicago Fire Department and ambulance services indicating that cases of TB, measles and other illnesses had existed long before this week.

City health officials have not identified how many TB cases have been confirmed or what shelters are involved. A health department spokesman did not respond to inquiries by NewsNation seeking those details.

Lopez accuses the city of playing a “smoke and mirrors game” and says he has been told that at least five TB cases have been linked to the same migrant shelter where the majority of measles cases have been linked since mid-March. He adds that the city “slow rolls” information to the public.

A spokesman for Johnson’s office did not respond to multiple requests for comment from NewsNation on Thursday.

The city health department said Wednesday that between 100 and 150 cases of TB are confirmed among Chicago residents each year. It’s planning a TB report for the city at large, which will be ready to release in the coming days.

Lopez said that incident tickets indicate that migrants were falling ill in August and September and that it became “painfully obvious” that not only did a health crisis exist among the migrant community but that Johnson did not want to recognize that issues existed.

He said cases of measles date back to December — when a record number of migrants were being sent to Chicago from the U.S. southern border by Texas GOP Gov. Greg Abbott.

In December, the city told the city council the number of measles cases remained small, that the cases were contained and that there was nothing to fret about, he said.

The healthiness of the city’s shelter system has been a concern since migrants began being sent to Chicago in late 2022, but the issue escalated when nearly 2,000 migrants were sent to local police precincts, where they slept in lobbies when the health ailments they suffered from became evident, Lopez said.

Lopez said he attempted to raise the issue but said he was met with claims from Johnson’s allies that he was projecting racist, xenophobic, anti-immigrant beliefs and that he was trying to hurt people by broaching the topic.

He maintains he was trying to save people, specifically migrants from Venezuela, which is traditionally the world’s least vaccinated people, according to the CDC.

Jacob Martin, a spokesman for the city’s health department, said that new arrivals are screened at the city’s landing zone for acute medical needs, including TB and measles.

This screening involves checking for specific symptoms that may indicate an infection of active TB or other illnesses. If indicated, new arrivals are then transported to the hospital from the landing zone for further evaluation and treatment.

Since the start of the measles outbreak, city health officials have vaccinated more than 5,000 migrants, who are now required to be vaccinated for measles, mumps and COVID-19 if they wish to remain in city-run shelters.

Lopez fears that as the city closes more of its 23 sponsored shelters in the coming weeks and months, health officials will see “a bump” in confirmed cases of illnesses as more migrants are blended into new spaces and the city works to consolidate where new arrivals are being housed.

However, Lopez feels like new arrivals should be vaccinated “to the American standard” — a call he said he issued last fall and winter — only to be ignored, he says. Since then, Lopez says that Johnson’s administration has attempted to limit the damage by not providing specifics about how many cases of illnesses exist.

“I think they know they’re already on very thin ice when it comes to public support for, especially in a city like Chicago, taxpayer-funded services being provided to these individuals, ” Lopez said. “And if we were to know the full scope of just how things are progressing — or not — you would see more of the public wanting an end to our operations.

“They would want to see us immediately end caring for these individuals who are often causing more problems than they are creating solutions for.”

As of Thursday, 9,764 migrants are being housed in city-run shelters.

An outbreak of measles was reported in mid-March, the majority of cases tied to the city’s largest migrant shelter in Chicago’s Pilsen neighborhood. Since then, the city has confirmed 56 measles cases, which brought a team from the Centers for Disease Control and Prevention to Chicago to investigate.

A CDC spokesman said the source of the measles cases remains under investigation. Chicago’s cases represent more than 50% of the 97 cases that have been confirmed nationally by the CDC.