What do the Levels Mean?
World Health Organization
Phase 1. No new influenza virus subtypes have been detected in humans. An influenza virus subtype which has caused human infection may be present in animals. If present in animals, the risk of human infection or disease is considered to be low.
Phase 2. No new influenza virus subtypes have been detected in humans. However, a circulating animal influenza virus subtype poses a substantial risk of human disease.
Phase 3. Human infection(s) with a new subtype, but no human-to-human spread, or at most rare instances of spread to a close contact.
Phase 4. Small cluster(s) with limited human-to-human spread but spread is highly localised, suggesting that the virus is not well adapted to humans.
Phase 5. Larger cluster(s) but human-to-human spread still localised, suggesting that the virus is becoming increasingly more adaptive to humans, but may not be fully transmissible (substantial pandemic risk).
Phase 6. Increased and sustained transmission in the general population.
Postpandemic period. Return to interpandemic period
State of Maine
Pre-pandemic / Interpandemic period - No new influenza virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection may be present in animals, or a circulating animal influenza poses a substantial risk of human disease.
Level I - Human infection(s) with a new subtype, but no human-to-human spread, or at most rare instances of spread to a close contact. (= WHO Phase 3)
Level II - Small cluster(s) with limited human-to-human transmission but spread is highly localized, suggesting that the virus is not well adapted to humans. (= WHO Phase 4)
Level III - Larger cluster(s) but human-to-human spread still localized, suggesting that the virus is becoming increasingly better adapted to humans, but may not yet be fully transmissible. (= WHO Phase 5)
Level IV - Pandemic Phase: Increased and sustained transmission in the general population. (= WHO Phase 6)
Level V - Post-Pandemic; Indices of influenza activity have returned to pre-pandemic levels.
Franklin Community Health Network (FCHN)
Pre-Pandemic - Same as Maine above
Level 1 - Alert Period (= Maine Level I above)
Level 2 - Evidence of pandemic flu outside of the United States (= Maine Levels II & III)
Level 3 - Evidence of pandemic flu in the United States (= Maine Levels II & III)
Level 4 - Evidence of pandemic flu in local area (Maine) (= Maine Levels II & III)
Level 5 - Increased and sustained transmission in the general population (= Maine Level IV)
Level 6 - Post Pandemic (= Maine Level V)
