In the US, a public health emergency (PHE) can be declared in response to a disease/disorder, significant infectious disease outbreak or bioterrorist attack:
The Secretary of the Department of Health and Human Services (HHS) may, under section 319 of the Public Health Service (PHS) Act, determine that: a) a disease or disorder presents a public health emergency (PHE); or b) that a public health emergency, including significant outbreaks of infectious disease or bioterrorist attacks, otherwise exists.
On January 31, 2020, the U.S. HHS made a PHE declaration in response to COVID and said that a public health emergency had existed since January 27, 2020. Since then, HHS has repeatedly renewed the PHE declaration, with the most recent renewal having been made on January 11, 2023.
A PHE declaration lasts either until "the [HHS] Secretary declares that the PHE no longer exists or upon the expiration of the 90-day period beginning on the date the Secretary declared a PHE exists, whichever occurs first."
News reports indicate that an end to the PHE may take place as soon as April 2023, though this depends on the COVID epidemiological situation. HHS Secretary Becerra has previously stated that HHS would to give a 60-day notice of the end of the PHE.