Bacteria are unicellular organisms that are much larger than viruses (10-100 times larger). They are capable of multiplying by themselves, as they have the power to divide. Their shapes vary, and doctors use these characteristics to separate them into groups. Bacteria are present everywhere in the biosphere, including inside and on the surface of human bodies. Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in the body (approximately 1014 versus 1013). The mass of microorganisms are estimated to account for 1-3% total body mass. Microbes inhabit just about every part of the human body, living on the skin, in the gut, and up the nose. Sometimes, if bacteria numbers grow beyond their typical ranges or if bacteria populate atypical areas of the body, they cause sickness, but most of the time, microorganisms live in harmony with their human hosts, providing vital functions essential for human survival. Like viruses, bacteria can also be aerosolized through coughing, sneezing, laughing or through close personal contact. These pathogens can travel through the air, causing diseases and worsening allergies or asthma. In a similar way to viruses, when someone sneezes or coughs, tiny water or mucous droplets filled with bacteria scatter.
Inhaling these bacteria can induce several diseases among which:
• Pneumonia (Streptococcus pneumoniae, Haemophilus influenzae)
• Tonsillitis (Beta haemolytic streptococcus)
• Tuberculosis (Mycobacterium tuberculosis)
• Diphtheria (Corynebakterium diphteriae)
• Pertussis (Bordetella pertussis)
• Epiglottitis, meningitis (Haemophilus influenzae)
• Meningitis (Neisseria meningitidis)
• Legionellosis, Pontiac fever (Legionella pneumophila)
Some bacteria thrive and circulate through poorly maintained building ventilation systems, as with Legionnaires’ disease (legionellosis).