Antibiotics are for the pneumonia that accompanies Flu and other viruses, H1N1 nearly killed my DD in 2009 when the bacteria got into her blood.
The messy goop Flu creates becomes very friendly to bacteria in the air and once it settles in the lungs, well, getting to the blood is a very small jump.
Diagnosed that Friday, we all got TamiFlu but by Monday she had both lungs filling with fluid and a blood infection.
Look for extreme lethargy, inability to stay upright, she became like a rag doll.
Watch for an inability to blow out, like to blow out a candle.
When it got into her blood Sunday night the fever would not budge, not with Tylenol or Motrin and not even with a lukewarm bath, which was my mom trick that always worked to help get a fever down a bit then fever would usually stay down with Motrin and Tylenol.
This was a different beast but I ignored my instincts because my pediatrician and pulmonary Dr went out of their way to make me feel like an panicky idiot.
Know when I learned the signs I am sharing? In the hospital quarantine after admitted, on my knees praying for 10 days by myself as DH managed DS. It would have been useful to know ahead of time.... I still hold that grudge - it reminds me to be vigilant. One lesson I will never forget.