Viruses cause colds. A runny nose often starts out with clear drainage and then turns to a green or yellow color. This is a good sign that the body is fighting the virus. An antibiotic will not help. If your runny nose is not getting better after 10-14 days, please talk to your doctor.
Viruses cause the flu.
Viruses cause most bronchitis. Viruses cause most sore throats. Only strep throat needs an antibiotic. A lab test can be done to see if group A strep bacteria are present. Group A strep bacteria cause strep throat.