The answer is bacteria
I hope this helps!
Breathing of contaminated air is the most common way, some can pass through the skin into the blood stream e,g acid
TB is highly contagious and can be transmitted from an infected person to an uninfected person, mainly when a person with TB coughs, sneezes, speaks, or even sings (known as airborne transmission or airborne disease). Other people who breathe in the aerosolized bacteria can become infected.
