Immediate danger? Call 911.
The correct action depends on the hazard. A respiratory illness spreading between people calls for different ventilation choices from an official warning of a dangerous outdoor release. Follow the current instructions from public-health and emergency officials, with the alert's date, affected area and requested action checked before forwarding it. [B01–B04]
Improve indoor air: when outdoor air is safe, increase fresh-air ventilation and consider a properly sized portable HEPA cleaner. Use a well-fitting mask or respirator when additional protection is needed. NIOSH-approved particulate respirators such as N95s filter particles; they do not filter hazardous gases or vapors. [B01, B03]
For common respiratory-virus symptoms, CDC's general community guidance is to stay home and away from others until, for at least 24 hours, both your symptoms have been improving overall and you have been fever-free without fever medicine. For the next 5 days, use added precautions such as cleaner air, masking, distance and testing around others. Some infections and settings have different rules. Seek prompt medical advice if at increased risk or symptoms worsen; call 911 for severe breathing difficulty or other life-threatening symptoms. [B02]
Stop handling it. Keep people away; do not shake, sniff, taste, open further, clean up or transport the material. Move away, wash hands with soap and water, and report the situation from a safe location. Call 911 for an immediate danger or medical emergency. For suspicious mail, Postal Inspectors can be reached at 1-877-876-2455; state that it is an emergency. Follow responder instructions about the room, clothing and decontamination. [B04, B07]
Do not diagnose a biological agent from a rash, a social-media photograph or a home gadget. Smallpox has been eradicated in nature; anthrax has different exposure routes and requires professional assessment. An official exposure warning may require prompt treatment before symptoms. Follow the specified eligibility and dispensing location rather than taking stored or borrowed antibiotics. For an anthrax dispensing site, bring each household member's medicine and allergy information and, for children, current weight, as officials request. [B05, B06, B08, B09]
Prepare now: keep current clinician and pharmacy contacts, a medication/allergy list, suitable masks, soap, a thermometer, and a plan for a sick person's care. Decide who can collect supplies without unnecessary contact. Write a short handover for a backup caregiver. These household planning steps do not replace disease-specific advice.
https://www.cdc.gov/respiratory-viruses/prevention/precautions-when-sick.html