>>> (d) Apprehension and examination of persons reasonably believed to be infected
>>> (1) Regulations prescribed under this section may provide for the apprehension and examination of any individual reasonably believed to be infected with a communicable disease in a qualifying stage and (A) to be moving or about to move from a State to another State; or (B) to be a probable source of infection to individuals who, while infected with such disease in a qualifying stage, will be moving from a State to another State. Such regulations may provide that if upon examination any such individual is found to be infected, he may be detained for such time and in such manner as may be reasonably necessary.
In many cases, the government has various powers like arresting, fining, or jailing people for violating quarantine or entering private property to investigate.
Always? That's just not true.
In the US, the CDC has the power to involuntarily quarantine AND EXAMINE people.
See their page about legal authority: https://www.cdc.gov/quarantine/aboutlawsregulationsquarantin...
Also, one of the relevant laws (https://www.govinfo.gov/content/pkg/USCODE-2011-title42/html...) says this:
>>> (d) Apprehension and examination of persons reasonably believed to be infected
>>> (1) Regulations prescribed under this section may provide for the apprehension and examination of any individual reasonably believed to be infected with a communicable disease in a qualifying stage and (A) to be moving or about to move from a State to another State; or (B) to be a probable source of infection to individuals who, while infected with such disease in a qualifying stage, will be moving from a State to another State. Such regulations may provide that if upon examination any such individual is found to be infected, he may be detained for such time and in such manner as may be reasonably necessary.
Health officials at the state level also have similar powers. Here's a summary of state-level laws: https://www.ncsl.org/research/health/state-quarantine-and-is...
In many cases, the government has various powers like arresting, fining, or jailing people for violating quarantine or entering private property to investigate.