When to Go to the Emergency Department for Flu
Patients with influenza should go to the emergency department if they have severe pneumonia indicators (CRB-65 score of 3 or more), bilateral chest signs of pneumonia, or any signs of respiratory failure including persistent hypoxia, confusion, respiratory rate ≥30/min, or blood pressure <90/60 mmHg. 1
Immediate ED Referral Criteria
Adults - Urgent Hospital Referral Required For:
CRB-65 score of 3 or 4 (high risk of death, >10% mortality) 1
- Score 1 point each for: Confusion, Respiratory rate ≥30/min, Blood pressure <90/60 mmHg, age ≥65 years 1
Bilateral chest signs (crackles on both sides) regardless of CRB-65 score, as this suggests primary viral pneumonia with rapid, fulminant course 1
Signs of respiratory failure: 1
- Oxygen saturation <90% on room air
- Persistent hypoxia with PaO₂ <8 kPa despite oxygen
- Progressive hypercapnia
- Severe acidosis (pH <7.26)
Septic shock (systolic BP <90 mmHg with signs of organ dysfunction) 1
New or worsening confusion (altered mental status) 1
Adults - Consider Hospital Assessment For:
CRB-65 score of 1 or 2 (particularly score 2, which carries 1-10% mortality risk) 1
New or worsening dyspnea (shortness of breath) not responding to initial treatment 1, 2
Recrudescent fever (fever returning after initial improvement, suggesting bacterial superinfection) 1, 2
Children - Urgent ED Referral For:
Children with any of the following severe illness indicators: 1, 2
- Breathing difficulties or respiratory distress
- Severe earache (suggesting otitis media complication)
- Vomiting for more than 24 hours (risk of dehydration)
- Drowsiness or altered consciousness
- Inability to maintain oral intake 1
Additional High-Risk Situations Requiring ED Evaluation
Unstable Clinical Factors (≥2 present):
Patients with two or more of these factors should seek ED care: 1, 2
- Temperature >37.8°C (100°F)
- Heart rate >100/min
- Respiratory rate >24/min
- Systolic blood pressure <90 mmHg
- Oxygen saturation <90%
- Inability to maintain oral intake
- Abnormal mental status
Special Populations at Lower Threshold:
The threshold for ED referral should be lower for: 1
- Patients with significant comorbidities (COPD, heart disease, diabetes)
- Frail or elderly patients
- Immunocompromised individuals
- Pregnant women 3
Common Pitfalls to Avoid
Do not delay ED presentation if bilateral chest signs are present, even with a low CRB-65 score—primary viral pneumonia can progress rapidly and has high mortality 1, 2
Do not assume improvement means recovery—recurrent fever after initial improvement suggests dangerous bacterial superinfection, particularly with Staphylococcus aureus, which carries high mortality 1, 2, 3
Do not rely solely on fever in elderly or immunocompromised patients—they may have severe illness without documented fever 1, 4
When Outpatient Management is Appropriate
Patients with CRB-65 score of 0 are at low risk (<1% mortality) and can typically be managed at home with: 1
- Self-care advice
- Antiviral therapy if presenting within 48 hours of symptom onset 4, 5
- Clear instructions on when to return for reassessment 2
Clinical judgment always supersedes scoring systems—social circumstances, ability to return if worsening, and access to care must be considered. 1