In the WHO pandemic phases, which phase is characterized by some human-to-human transmission being evident?

• A. Phase 1
• B. Phase 3
• C. Phase 6
• D. Phase 4

Answer: (D)

Understanding when human-to-human transmission becomes evident marks a turning point in how we view an outbreak. At this stage, investigators have confirmed that the virus can pass between people and that transmission is occurring beyond isolated cases, though it may still be limited to specific areas and not yet widespread globally. This signals that the outbreak is moving from animal-to-human events toward human-to-human spread, triggering increased surveillance and response preparations.

That’s why the phase described as having some human-to-human transmission being evident is the correct one: it reflects the first clear indication that people can transmit the virus to others, even if the spread isn’t yet broad or sustained across regions.