Found this:

Infectious Period:
The duration of contagiousness varies based on the specific infection, and the length of time for an infection to be no longer contagious after starting antibiotics can range from 48 hours to 14 days.
Azithromycin and Asthma:
Azithromycin is sometimes used in asthma management, especially for severe asthma cases, to help reduce exacerbations and manage inflammation.
Antibiotic Courses:
The length of an azithromycin course can range from 3 to 10 days, depending on the specific infection.
Not Routine Use:
Antibiotics are generally not routinely used for acute asthma exacerbations unless there is evidence of a bacterial infection, according to guidance from National Institutes of Health (NIH).

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Mine is 5 days with the first dose being double plus 5 days of prednisone 40 mg each day.

Also found:

A bacterial infection in a person with asthma can exacerbate their symptoms, including cough, shortness of breath, and wheezing. Additional symptoms of a bacterial infection might include fever, chills, fatigue, and possibly yellow or green phlegm.