State health officials are investigating a tuberculosis outbreak that is thought to have started at Minnesota State University-Mankato.

The Minnesota Department of Health says it's looking into the eight cases among people who had spent time at the college since 2016.

The risk of TB spreading among the public is low, it says, because it requires "close, prolonged contact" with an infected person for it to spread.

Nonetheless it has advised anyone who had been at the college since August 2016 to be aware of the possible symptoms, which include fatigue, loss of appetite, chest pain and a persistent cough.

It's thought that the infection first came via an international student and then spread to others who had close contact with them, according to the Star Tribune, which notes that most of those affected are MSU students or former students.

Around 700 people who have been in contact with those infected have been contacted by the state health department, the newspaper adds.

The Mankato Free Press notes that Blue Earth County only had three TB cases in 2016 and 2017.

It is one of the world's biggest killers, infecting around 10 million people every year.

But the number of cases in the United States hit its lowest number on record in 2017, when just 9,105 cases were reported. However, there was an increase in TB deaths at 528, compared to 470 in 2016.

The Centers for Disease Control says that of the American residents infected last year, 70.1 percent were not born in the U.S., with the disease more commonly contracted by those who travel or who were born in countries with high TB rates.

An estimated two billion people have the TB infection, but in the vast majority it exists in a latent form, whereby the bacteria remains in the body in an inactive state and causes no symptoms, though it can turn into active TB, the Mayo Clinic notes.

The disease mainly attacks your lungs and can be fatal when untreated.