|
Inter-pandemic phase
New virus in animals, no human cases |
No new influenza virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection may be present in animals. If present in animals, risk of human infection or disease is considered to be low. |
1 |
| No new influenza virus subtypes have been detected in humans. However, a circulating animal influenza virus subtype poses a substantial risk of human disease. |
2 |
|
Pandemic alert
New virus causes human cases |
Human infection(s) with a new subtype, but no human-to-human spread, or at most rare instances of spread to a close contact. |
3 |
| Small cluster(s) with limited human-to-human transmission but spread is highly localized, suggesting that the virus is not well adapted to humans. |
4 |
| 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 (substantial pandemic risk). |
5 |
| Pandemic |
Pandemic: increased and sustained transmission in general population. |
6 |
Source: World Health Organization (WHO)
Colors: Current WHO phase of pandemic alert
Text: WHO Global Influenza Preparedness Plan |
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