Reportable diseases are diseases considered to be of great public health importance. Local, state, and national agencies (for example, county and state health departments or the U.S. Centers for Disease Control and Prevention) require that such diseases be reported when they are diagnosed by doctors or laboratories.

Reporting allows for the collection of statistics that show how often the disease occurs. This, in turn, helps researchers identify disease trends and track disease outbreaks. This can help control future outbreaks.

All states have a "reportable diseases" list. It is the responsibility of the health care provider, not the patient, to report cases of these diseases. Many of the diseases on the lists must also be reported to the U.S. Centers of Disease Control (CDC).

Reportable diseases are divided into several groups:

• Mandatory written reporting: This means a report of the disease must be made in writing. Examples are gonorrhea and salmonellosis.
• Mandatory reporting by telephone: This means the health care provider must make a report by phone. Examples are rubeola (measles) and pertussis (whooping cough).
• Report of total number of cases: Examples are chickenpox and influenza.
• Cancer: Cancer cases are reported to the state Cancer Registry.

A typical state list may appear as follows. Diseases marked with an asterisk (*) were reportable to the CDC at the national level in 2006:

• Acquired Immunodeficiency Syndrome (AIDS)*
• Anthrax *
• Arboviral diseases (diseases caused by viruses spread by mosquitoes, sandflies, ticks, etc.)
  • California serogroup virus disease
  • Eastern equine encephalitis
  • Powassan virus disease
  • St. Louis encephalitis
  • West Nile virus
  • Western equine encephalitis
• Botulism *
• Brucellosis *
• Chancroid *
• Chickenpox
• Chlamydia trachomatis (genital infection)*
• Cholera *
• Coccidioidomycosis *
• Diphtheria *
• Echinococcosis
• Ehrlichiosis *
• Flu-related infant deaths
• Giardiasis *
• Gonorrhea*
• Haemophilus influenza, invasive disease
• Hantavirus pulmonary syndrome*
• Hemolytic uremic syndrome, post-diarrhea
• Hepatitis A *
• Hepatitis B *
• Hepatitis C*
• HIV infection*
• Influenza A virus infections - novel
• Legionellosis*
• Listeriosis*
• Leprosy (Hansen's disease)*
• Lyme disease*
• Malaria *
• Measles*
• Meningococcal disease*
• Mumps *
• Pertussis *
• Plague *
• Poliomyelitis *
• Poliovirus infection, nonparalytic
• Psittacosis*
• Q-fever*
• Rabies (human and animal cases) *
• Rocky Mountain spotted fever *
• Rubella (including congenital syndrome)*
• Salmonellosis*
• Severe acute respiratory syndrome (SARS) *
• Shiga toxin-producing Escherichia coli (STEC)*
• Shigellosis *
• Smallpox*
• Streptococcal disease, invasive, Group A*
• Streptococcus pneumonia, drug resistant and invasive, including invasive cases in children age 5 and younger*
• Syphilis, including congenital syphilis*
• Tetanus *
• Toxic shock syndrome - Staphylococcus bacteria*
• Toxic shock syndrome - Streptococcus bacteria*
• Trichinosis *
• Tuberculosis *
• Tularemia *
• Typhoid fever*
• Vancomycin intermediate Staphylococcus aureus (VRSA)*
• Vancomycin resistant Staphylococcus aureus (VRSA)*
• Vibrosis
• Yellow fever *

The state health department will attempt to find the source of many of these illnesses, such as food poisoning or amebiasis. In the case of sexually-transmitted diseases (STD) the state will attempt to locate sexual contacts to assure they are disease-free or are appropriately treated if they are already infected.

The information obtained by reporting allows the state to make informed decisions and laws concerning activities and the environment such as food handling, water purification, insect control, animal control, STD tracking, and immunization programs.

Please remember that the health care provider is bound by law to report these events. People with any of the diseases listed in the state's reporting schedule should make every effort to cooperate with the state health workers. Cooperation may help locate the source of an infection or prevent the spread of an epidemic.