The difference between negative and positive TB is the sputum test; positive sputum is positive for TB and negative sputum is negative for TB. Positive patients are infectious, while negative patients are not infectious. The sputum test includes sputum culture and sputum smear. A positive sputum culture for Mycobacterium tuberculosis or a positive sputum smear for Mycobacterium antacidum is considered positive. Patients with positive sputum can cough, sneeze, speak, sing, or laugh and spread microscopic droplets of Mycobacterium tuberculosis into the air, where they can stay for several hours and be easily infected when inhaled by others. When coughing or sneezing, TB patients should also be careful to cover themselves to avoid spreading the virus into the air.