Yes, You Remain Contagious After Symptoms Resolve
Even without active diarrhea or vomiting, you are still infectious with norovirus for 24-72 hours after your symptoms completely resolve, and viral shedding can continue for an average of 4 weeks, though the degree of infectivity during this extended period is less clear. 1, 2
Contagious Period After Symptom Resolution
Infectivity can last for as long as 2 days after resolution of symptoms, according to CDC guidelines. 3 More recent guidance specifies:
- Exclude ill individuals from work or group activities for 48-72 hours after complete symptom resolution to prevent transmission 1, 2
- In institutional settings (hospitals, nursing homes), isolation should continue for 24-48 hours after symptoms cease 1, 2
- This recommendation applies to healthcare workers, food handlers, and childcare workers who pose higher transmission risk 1, 2
Viral Shedding Timeline
The infectious period extends well beyond when you feel better:
- Peak viral shedding occurs 2-5 days after infection, with approximately 100 billion viral copies per gram of feces 1, 4
- Viral shedding continues for an average of 4 weeks following infection, though infectivity beyond the acute symptomatic phase remains unclear 1, 2, 4
- The virus requires only 10-100 viral particles to cause infection, making even low-level shedding potentially infectious 4
Why This Matters at 36 Hours Post-Onset
At 36 hours after symptom onset, you are likely:
- Still within the peak viral shedding window (2-5 days post-infection) 1, 4
- Highly contagious even if symptoms have improved or resolved 3, 1
- Capable of transmitting virus through multiple routes: person-to-person contact, contaminated surfaces (fomites), and potentially aerosolized particles from prior vomiting 3, 5
Critical Infection Control Measures
Handwashing with soap and running water for at least 20 seconds is the most effective method to reduce norovirus contamination on hands—alcohol-based sanitizers cannot replace this for norovirus. 1, 2
Additional precautions while still contagious:
- Avoid preparing food for others until at least 48-72 hours after symptoms resolve 1, 2
- Avoid close contact with vulnerable populations (elderly, immunocompromised, young children) 1
- Clean and disinfect contaminated surfaces with chlorine bleach solution at 1,000-5,000 ppm (1:50 to 1:10 dilution of household bleach) 1
- Do not return to healthcare, food service, or childcare work until 48-72 hours symptom-free 1, 2
Common Pitfall to Avoid
The most dangerous misconception is assuming you are no longer contagious once you feel better. The typical illness duration is only 12-72 hours in healthy adults 2, 4, but this does not correlate with when viral shedding stops. Many secondary transmissions occur from individuals who have recovered symptomatically but remain infectious. 3
Special Considerations
- Up to 30% of norovirus infections are asymptomatic, yet these individuals still shed virus at lower titers and can transmit infection 4
- Immunocompromised patients can shed virus for months to years, representing a severe and prolonged infectious state 1, 2
- Presymptomatic transmission is possible during the 24-48 hour incubation period before symptoms appear 4