ICD-10 Code for Exposure to Whooping Cough
The ICD-10 code for exposure to whooping cough (pertussis) is Z20.7 (Contact with and exposure to pediculosis, communicable diseases, and other infections), though this is not specific to pertussis alone; the more appropriate code is Z20.811 (Contact with and (suspected) exposure to other bacterial communicable diseases).
Understanding ICD-10 Coding for Pertussis Exposure
Primary Exposure Code
- Z20.811 is the most appropriate ICD-10 code for documenting contact with or suspected exposure to pertussis, as it specifically addresses exposure to bacterial communicable diseases 1.
Important Clinical Context
When coding for pertussis exposure, it is critical to distinguish between exposure without infection (Z20.811) versus confirmed or suspected active infection (A37.0 for confirmed Bordetella pertussis or A37.9 for unspecified whooping cough) 2, 3.
The exposure code should be used for asymptomatic individuals who have had close contact with a confirmed pertussis case, particularly when they are receiving post-exposure prophylaxis 1.
Clinical Management Following Exposure
Post-Exposure Prophylaxis Indications
All household and close contacts of confirmed pertussis cases should receive antibiotic prophylaxis for 14 days, regardless of age and vaccination status, as recommended by the Centers for Disease Control and Prevention 4.
Prophylaxis is most effective when initiated promptly after exposure, particularly for high-risk contacts including infants <12 months, pregnant women in the third trimester, and healthcare workers 4, 5.
Recommended Prophylactic Regimens
First-line prophylaxis is a macrolide antibiotic: azithromycin (500 mg day 1, then 250 mg daily for 4 days in adults; 10 mg/kg day 1, then 5 mg/kg daily for 4 days in children) 4, 6.
Alternative options include erythromycin for 14 days (1g/day for adults, 40-50 mg/kg/day for children) or clarithromycin for 10-14 days (500 mg twice daily for adults, 15-20 mg/kg/day in two divided doses for children) 4.
For patients with macrolide hypersensitivity or intolerance, trimethoprim-sulfamethoxazole for 14 days is recommended (320mg/1600mg per day for adults, 8mg/40mg/kg/day for children) 4.
Work/School Exclusion Guidelines
Asymptomatic healthcare workers or individuals receiving chemoprophylaxis after pertussis exposure do not need to be excluded from work or patient care, according to CDC guidelines 1.
However, if an exposed individual is unable to receive chemoprophylaxis and is asymptomatic, exclusion from caring for children <4 years may be required from 7 days after first exposure until 14 days after last exposure, particularly if mandated by state law 1.
Common Coding Pitfalls
Avoid Misclassification
Do not use active disease codes (A37.0 or A37.9) for asymptomatic exposed individuals, as this misrepresents the clinical scenario and may affect treatment decisions 2, 3.
ICD-9 codes (033.x series) have shown poor sensitivity (38.6%) and moderate specificity (76.9%) for identifying laboratory-confirmed pertussis, highlighting the importance of proper documentation and coding practices 2.
Documentation Requirements
Clearly document the exposure circumstances, including the date of exposure, relationship to the index case, and whether prophylaxis was initiated 1.
Note that pertussis remains highly contagious, with secondary attack rates exceeding 80% among susceptible household contacts, making proper coding and prophylaxis critical 4, 7.