Infectious Disease Epidemiology Program

Airborne and Direct Contact Diseases

Airborne Diseases

Airborne diseases are caused by pathogenic microbes small enough to be discharged from an infected person via coughing, sneezing, laughing and close personal contact or aerosolization of the microbe.  The discharged microbes remain suspended in the air on dust particles, respiratory and water droplets. Illness is caused when the microbe is inhaled or contacts mucus membranes or when secretions remaining on a surface are touched.  

Transmission of airborne diseases can be greatly reduced by practicing social and respiratory etiquette. Staying home when ill, keeping close contact with an ill person to a minimum, allowing a few feet distance from others while ill, and wearing a mask, covering coughs and sneezes with elbow or tissue can greatly reduce transmission. Good hand washing can decrease spread of germ-containing droplets that could be picked up on hands from surfaces or hand contact with secretions.  Environmental controls and engineering alternatives help reduce transmission of water droplet aerosolized pathogens.

Contact Diseases

Contact Diseases are transmitted when an infected person has direct bodily contact with an uninfected person and the microbe is passed from one to the other. Contact diseases can also be spread by indirect contact with an infected person’s environment or personal items. The presence of wound drainage or other discharges from the body suggest an increased potential for risk of transmission and environmental contamination.  Precautions that create a barrier and procedures that decrease or eliminate the microbe in the environment or on personal belongings, form the basis of interrupting transmission of direct contact diseases.  

  • Anthrax - A serious disease caused by Bacillus anthracis, a bacterium that forms spores. A bacterium is a very small organism made up of one cell. Many bacteria can cause disease. A spore is a cell that is dormant (asleep) but may come to life with the right conditions.
  • Coronavirus - Coronaviruses are a large family of viruses that includes viruses that may cause a range of illnesses in humans, from the common cold to SARS and MERS.
  • Group A Streptococcus - A bacterium often found in the throat and on the skin. People may carry group A streptococci in the throat or on the skin and have no symptoms of illness. Most GAS infections are relatively mild illnesses such as "strep throat," or impetigo. Occasionally these bacteria can cause severe and even life-threatening diseases.
  • Invasive Group B Streptococcal (GBS) - A bacterium that causes illness in newborn babies, pregnant women, the elderly, and adults with other illnesses, such as diabetes or liver disease. GBS is the most common cause of life-threatening infections in newborns.
  • Haemophilus influenza - Invasive disease caused by Haemophilus influenzae type b can affect many organ systems. The most common types of invasive disease are pneumonia, occult febrile bacteremia, meningitis, epiglottitis, septic arthritis, cellulitis, otitis media, purulent pericarditis, and other less common infections such as endocarditis, and osteomyelitis.
  • Legionellosis - An infection caused by the bacterium Legionella pneumophila. Maine monitors the incidence of Legionellosis through mandatory reporting by health care providers, clinical laboratories and other public health partners.
  • Meningococcal Disease - The leading cause of bacterial meningitis in children and young adults in the United States. Symptoms of meningococcal disease include fever, headache and stiff neck in meningitis cases, and sepsis and rash in meningococcemia.
  • MERS-CoV - Currently, all cases are associated with either direct travel to the Arabian peninsula, or contact with a returned traveler from the Arabian peninsula.
  • MRSA - Methicillin-resistant Staphylococcus Aureus is a bacterial infection that is resistant to some antibiotics. When MRSA bacteria are found on the skin but do not cause illness it is called "colonization." In most cases, MRSA does not cause any problems or causes minor infections, such as pimples or boils. In some cases, MRSA can cause more serious infections.
  • Plague - Plague is a disease caused by Yersinia pestis (Y. pestis), a bacterium found in rodents and their fleas in many areas around the world.
  • Strep pneumoniae - a Gram-positive encapsulated coccus that often colonizes the human nasopharynx, where it can be carried asymptomatically.
  • SARS - respiratory disease caused by a coronavirus, last reported in 2004