International phases and their significance for the UK
| International phases | Significance for UK | ||
|---|---|---|---|
| Interpandemic period | |||
| 1 | No new influenza virus subtypes detected in humans | ||
| 2 | Animal influenza virus subtype poses substantial risk | UK not affected | |
| UK has strong travel/trade connections with affected country | |||
| UK affected | |||
| Pandemic alert period | |||
| 3 | Human infection(s) with a new subtype, but no new human to human spread to a close contact | UK not affected | |
| 4 | Small cluster(s) with limited human-to-human transmission but spread is highly localised, suggesting that the virus is not well adapted to humans | UK has strong travel/trade connections with affected country | |
| 5 | Large cluster(s) but human-to-human spread still localised, suggesting that the virus is becoming increasingly better adapted to humans | UK affected | |
| Pandemic period | |||
| 6 | Increased and sustained transmission in general population | Alert level | |
| 1 | Virus/cases only outside the UK | ||
| 2 | Virus isolated in the UK | ||
| 3 | Outbreak(s) in the UK | ||
| 4 | Widespread activity across the UK | ||
| Post pandemic period | |||
| Return to interpandemic period | |||