The new cases increase the number of deaths to four and the toll of residents sickened to 29 at the Quincy veterans’ home. Testing is ongoing for other residents. The outbreak at the home in Quincy, about 300 miles southwest of Chicago, was first reported last week.

On Sunday, the department requested aid from the U.S. Centers for Disease Control and Prevention, and specialists were sent to investigate the outbreak. CDC officials referred inquiries to their Illinois counterparts.

Legionnaires’ disease, a severe form of pneumonia, is caused by inhaling mist infected with the bacteria Legionella. “But when a cluster of people get sick like this, it’s very likely there’s one source point”.

The source of the disease has not been determined, but Drummond said the health department is confident it’s contained to the veterans’ home.

It doesn’t spread from person-to-person, but rather through the air, with those getting it typically coming down with a fever, chills and a cough. Additional symptoms include: headache, fatigue, loss of appetite, confusion and diarrhea.

In 2014, almost 6 percent of full-time students surveyed by researchers said they had used marijuana every day or at least 20 times in the previous 30 days, while 5 percent said they were heavy cigarette smokers, the Associated Press reported.

On Friday, the state announced that an inmate at the San Francisco-area prison was diagnosed with the disease and about 20 others showed symptoms of pneumonia, prompting officials to shut off water service at the institution. People who are older than 50, current or former smokers, and people with chronic lung diseases and weakened immune systems are more vulnerable to serious complications. Access by outsiders is otherwise not limited, and residents are not being restricted from leaving the home.