When you are sick (especially when you have a fever), you sometimes feel the cold as if it were colder than it actually is. [[]{}]( means this feeling of coldness. It does not matter whether it is caused by viruses or bacteria, nor does it matter whether it is for a short period or for a long period. As Chocolate noted, it also means the similar feeling caused by fear. The word “chill” in English has a similar meaning.
(Do not confuse with a separate word [[]{}]( which is written in the same way in kanji.)