Contagious diseases abound in the human population, perpetuated by person-to-person transmission through varied forms of contact. The route of transmission typically correlates to the primary site of the infection, although some contagious diseases have more than one route of entry. Community-based and personal infection control practices can decrease the risk for contracting contagious diseases and transmitting illnesses to others.
Fecal-Oral Diseases
Many viral, bacterial and parasitic diseases are transmitted from person to person via a fecal-oral route. Disease-causing organisms are expelled in the feces of an infected person. The feces then contaminates the food or water of other individuals, gaining entry to the body through inadvertent consumption. On a community level, stool-contaminated drinking water or farming soil can cause infection of large numbers of people. Poor personal hygiene, such as not washing the hands after a bowel movement or before preparing food, can sicken those in an infected person's family or work environment. The medical reference text "Principles and Practice of Infectious Diseases" reports that contagious diseases typically spread by a fecal-oral route include bacillary dysentery, amebic dysentery, cholera, salmonellosis, shigellosis, typhoid fever, cryptosporidiosis, giardiasis, hepatitis A and viral gastroenteritis caused by rotavirus, norovirus and many other viral species.
Sexually Transmitted Diseases
Sexually transmitted diseases continue to threaten personal and community health. These contagious diseases are contracted through sexual contact, including vaginal or anal intercourse and oral sex. Sexually transmitted diseases often cause few symptoms, which may lead to unwitting transmission of infection to others due to lack of awareness when an infection is present. Sexually transmitted contagious diseases noted by the U.S. Centers for Disease Control and Prevention include syphilis, chlamydia, gonorrhea, lymphogranuloma venereum, genital warts, chancroid, genital herpes, bacterial vaginosis, pelvic inflammatory disease and trichomoniasis. HIV and hepatitis B are blood-borne diseases that are commonly transmitted through sexual contact. Sexual contact can also serve as an uncommon route of transmission for the blood-borne hepatitis C virus.
Respiratory Diseases
Viral respiratory illnesses are notoriously contagious. The sneezing, coughing and runny nose associated with these infections are not only symptoms but mechanisms of viral spread. The nasal and airway secretions of someone infected with a respiratory virus teem with infectious viral particles. The viruses often pass from person to person through an inanimate intermediate. For example, people often sneeze or cough into their hands--and then touch many surfaces, effectively contaminating all of them. Unsuspecting persons who touch a contaminated surface often pick up the viruses. Less commonly, inhaling infectious droplets produced by the coughing or sneezing of a nearby person can lead to infection. "Principles and Practice of Infectious Diseases" lists many contagious viral respiratory illnesses, including head colds, sore throats, influenza, viral bronchitis and viral pneumonia.
References
- "Principles and Practice of Infectious Diseases, Sixth Edition"; Gerald L. Mandell, M.D., et al., Editors; 2004
- U.S. Centers for Disease Control and Prevention: Most Common Foodborne Diseases
- U.S. Centers for Disease Control and Prevention: Water-Related Diseases, Contaminants, and Injuries By Type
- U.S. Centers for Disease Control and Prevention: Sexually Transmitted Diseases in the United States--2008, National Surveillance Data for Chlamydia, Gonorrhea, and Syphilis
- U.S. Centers for Disease Control and Prevention: Sexually Transmitted Diseases in the United States--2008, Other Sexually Transmitted Diseases (STDs)
