It's not about actual fire, but about fast transmission of information or trends.

Figurative Use

Often used for controversial or shocking updates that grab people's attention.

Negative News

Can carry a sense of urgency or excitement related to the shared information.

The idiom can describe the rapid expansion of actual fires, often exacerbated by conditions such as wind.

Used metaphorically to describe how quickly diseases can infect large numbers of people.

Denotes something that is hard to control once it has begun spreading.