"Onlookers"

This is the paragraph (from cnn.com ):

Experts predicted that the country could expect millions of coronavirus cases. Doctors warned that India needed to prepare for an onslaught of cases that could cripple the country's ill-equipped health system. Onlookers worried that the virus could spread like wildfire through India's slums, where residents live in cramped quarters and basic sanitation often isn't available.

I wonder whom exactly the article refers to by onlookers.

The dictionary states onlookers are people who watch a situation without taking part on it.

So I suppose the onlookers here aren't the slum residents.

Are the onlookers Are they just residents, passers-by who witness the problem or are they authorities, specialists sharing their view from outside the situation?

Thanks!

Edit: The system did not post this correctly. I was unable to answer it as posted. This is a copy. CJ