4 doctors weighed in:
How can I differentiate between the flu and a sinus infection? I gave had the flu before with no fever
4 doctors weighed in

Dr. Robert Kwok
Pediatrics
3 doctors agree
In brief: Usually need a test
To tell if a person has the flu, he needs a rapid flu test which is a swab from the inside of the nose (deep in the nose), and takes 10-15 minutes to get a result.
It is pretty accurate during the first 1-3 days of flu symptoms, and is very helpful in deciding what medication should be used. For people without high fever and muscle aches in flu season, it is not that easy to guess who has the flu.

In brief: Usually need a test
To tell if a person has the flu, he needs a rapid flu test which is a swab from the inside of the nose (deep in the nose), and takes 10-15 minutes to get a result.
It is pretty accurate during the first 1-3 days of flu symptoms, and is very helpful in deciding what medication should be used. For people without high fever and muscle aches in flu season, it is not that easy to guess who has the flu.
Dr. Robert Kwok
Dr. Robert Kwok
Thank
Get help from a real doctor now
Dr. William Forsythe
Board Certified, Emergency Medicine
23 years in practice
171K people helped
Continue
107,000 doctors available
Read more answers from doctors