Communicable Diseases
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Communicable diseases are infectious diseases that are spread from person to person – such as E. coli, Salmonella or chickenpox – or from animals to people, like rabies or H1N1 flu. Cook County Department of Public Health prevents the spread of infectious diseases through disease surveillance, community education, outbreak response and by providing recommendations to control the spread of communicable diseases in suburban Cook County. Click on the buttons below to learn more about reportable diseases, sexually transmitted diseases, vaccine preventable diseases, immunizations and tuberculosis, as well as disease case counts, data reports and resources.
Communicable Diseases
COVID
COVID is an infectious disease caused by a virus that infects the lungs and breathing passages, such as the nose, mouth, and throat. It can cause mild to severe respiratory illness, including dry cough, shortness of breath, fatigue, fever, diarrhea, head and body aches, and loss of taste and/or smell.
Cyclosporiasis
Cyclosporiasis is an infectious disease caused by a parasite called Cyclospora. Most people infected with Cyclospora develop watery diarrhea, stomach cramping, bloating or increased gas, fatigue, and nausea. Symptoms typically start around seven days after ingesting the parasite. Sometimes people infected with Cyclospora will have no symptoms at all.
Flu
Influenza (flu) is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. Influenza A and B viruses routinely spread in people between October and March every year.
H5N1 Bird Flu
Highly pathogenic avian influenza A(H5N1), also known as H5N1 or bird flu, is a viral disease that primarily infects poultry (e.g., chickens, turkey, ducks), wild birds and U.S dairy cows.
Hepatitis B
Hepatitis B is a serious liver infection that can lead to liver failure and cancer.
Measles
Measles is a serious respiratory disease (in the lungs and breathing tubes). It causes a rash and fever. It is very contagious. In rare cases, it can be deadly.
Mpox
Mpox (previously known as monkeypox) is a viral infection caused by the mpox virus, related to smallpox but usually less severe. Mpox can affect anyone regardless of gender or sexual orientation. Early identification, testing, and treatment helps stop mpox from spreading.
Rabies
Rabies is a deadly virus spread to people from the saliva or neural tissue (i.e., brain, spinal cord) of infected animals. Only mammals can get rabies. Once a person begins showing signs and symptoms of rabies, the disease is nearly always fatal. For that reason, immune globulin and rabies vaccine is recommended under certain circumstances to stop the rabies virus from infecting the body.
Reportable Diseases & Conditions
Determine if a disease is reportable, and in which timeframe it should be reported — Immediately (within 3 hours), within 24 hours, or within 3 days.
Respiratory Syncytial Virus Infection (RSV)
Respiratory syncytial virus, or RSV, is a common respiratory virus that usually causes mild, cold-like symptoms. Most people recover in a week or two, but RSV can cause serious illness in some people, especially for infants and older adults.
Sexual Health and STI/HIV Prevention
Sexually transmitted infections (STIs), also known as STDs, refer to many different infections spread most commonly through sexual activity. The most prominent STIs are gonorrhea, chlamydia, syphilis, Mpox, and HIV, all of which are reportable conditions and require investigation by local health departments. Other common STIs include herpes, human papilloma virus (HPV, causing genital warts), hepatitis B, mycoplasma genitalium, and trichomoniasis.
Tuberculosis
Tuberculosis is an infection caused by the bacteria Mycobacterium tuberculosis, which spreads from person to person when a contagious individual sneezes, coughs, or speaks and the TB germs are inhaled by others.
Vaccine Preventable Diseases
Vaccine-preventable diseases are infections caused by viruses or bacteria that can be avoided through safe, effective immunization. They include illnesses such as measles, mumps, rubella, polio, whooping cough (pertussis), diphtheria, tetanus, hepatitis B, influenza, and chickenpox, many of which once caused widespread sickness, disability, and death, especially among young children.
West Nile Virus
West Nile virus is a mosquito-borne illness and the leading cause of mosquito-borne disease. It is spread mainly through the bite of infected Culex mosquitoes, which pick up the virus by feeding on infected birds, and cases typically rise from summer through early fall when mosquitoes are most active.
Data & Reports
Communicable Disease Case Counts
Data for vaccine preventable diseases, selected communicable diseases, and sexually transmitted infections in suburban Cook County.
Communicable Disease Data Dashboards
The Cook County Department of Public Health has created a series of interactive data visualization applications on topics of special interest.
Communicable Disease Data & Reports
Comprehensive population, health behavior, disease and injury data for residents of suburban Cook County.
Cook County Health Atlas
A wealth of data to help you understand, describe and address health issues in your community.
Epidemiology Data & Reports
Track health trends, hospital visits, and factors like housing, income, and environment.
Updated November 4, 2026, 2:26 PM