Communicable Disease Case Counts
Communicable disease case counts are shown below for vaccine preventable diseases, selected communicable diseases, and sexually transmitted infections in suburban Cook County. Case counts are provided quarterly for the current year only.
| Vaccine Preventable Diseases | 2026-Q3* | 2025 | 2024 | 2023 | 2022 | 2021 | 5-yr Median |
|---|---|---|---|---|---|---|---|
| Diphtheria | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Haemophilus Influenzae†| 32 | 50 | 46 | 43 | 36 | 16 | 43 |
| Hepatitis B (Acute) | 3 | 12 | 9 | 3 | 8 | 4 | 8 |
| Hepatitis B (Chronic) | 159 | 235 | 265 | 309 | 259 | 353 | 265 |
| Measles | 1 | 5 | 2 | 5 | 0 | 0 | 2 |
| Mumps | 0 | 1 | 2 | 7 | 5 | 2 | 2 |
| Pertussis (Whooping Cough) | 75 | 174 | 630 | 280 | 15 | 8 | 174 |
| Pneumococcal Disease (Invasive)¶ | 5 | 5 | 6 | 6 | 3 | 2 | 5 |
| Rubella | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Tetanus | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Varicella (Chickenpox) | 44 | 79 | 58 | 58 | 39 | 30 | 58 |
| Selected Communicable Diseases | 2026-Q3* | 2025 | 2024 | 2023 | 2022 | 2021 | 5-yr Median |
|---|---|---|---|---|---|---|---|
| Campylobacteriosis | 376 | 464 | 421 | 358 | 309 | 271 | 358 |
| Cryptosporidiosis | 61 | 59 | 76 | 48 | 67 | 40 | 59 |
| E.coli O157:H7 | 6 | 8 | 7 | 9 | 4 | 7 | 7 |
| Hepatitis A | 0 | 5 | 6 | 9 | 8 | 3 | 6 |
| Hepatitis C (Chronic) | 202 | 314 | 381 | 357 | 428 | 578 | 381 |
| Histoplasmosis | 37 | 32 | 48 | 29 | 22 | 41 | 32 |
| Legionnaires' Disease | 106 | 80 | 114 | 111 | 92 | 145 | 111 |
| Listeriosis | 5 | 10 | 12 | 11 | 4 | 5 | 10 |
| Lyme Disease | 65 | 97 | 58 | 69 | 27 | 116 | 69 |
| Malaria | 5 | 7 | 17 | 12 | 11 | 7 | 11 |
| Meningococcal Disease | 2 | 3 | 1 | 1 | 0 | 1 | 1 |
| Salmonellosis | 335 | 409 | 364 | 289 | 275 | 260 | 289 |
| Shigellosis | 88 | 101 | 110 | 87 | 83 | 54 | 87 |
| Tuberculosis | 73 | 86 | 70 | 75 | 65 | 62 | 70 |
| Typhoid Fever | 2 | 4 | 5 | 7 | 11 | 4 | 5 |
| West Nile Virus (Neuroinvasive) | 13 | 33 | 16 | 37 | 9 | 16 | 16 |
| West Nile Virus (Non-Neuroinvasive) | 11 | 11 | 3 | 2 | 0 | 4 | 3 |
| Sexually Transmitted Infections | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 5-yr Median |
|---|---|---|---|---|---|---|---|
| Chlamydia | ** | 10,806 | 10,942 | 11,132 | 10,507 | 12,234 | 10,942 |
| Gonorrhea | ** | 3,061 | 3,241 | 3,932 | 3,952 | 3,536 | 3,536 |
| HIV (Any Stage) | ** | 211 | 239 | 265 | 214 | 271 | 239 |
| Syphilis§ | ** | 157 | 159 | 204 | 167 | 170 | 167 |
Excludes Chicago, Evanston, Oak Park, Skokie and Stickney Township. For tuberculosis, excludes Chicago only.
* Provisional cases through the third quarter of 2026
†Includes type B
¶ Reportable only in those under 5 years of age
§ Primary and secondary syphilis
** Due to reporting lags, data are not available
Updated October 20, 2026, 9:38 AM