Two classes of medicines that fight infection: antibiotics act against bacteria, while antivirals act against viruses.
- Antibiotics kill or stop the growth of bacteria, for example penicillin (the first antibiotic, discovered by Alexander Fleming in 1928 from the mould Penicillium), but they have no effect on viruses such as those causing the common cold or influenza.
- Antivirals interfere with a virus's ability to enter cells or to multiply; examples include oseltamivir for influenza and acyclovir for herpes, and they are usually specific to particular viruses.
- Antibiotic resistance arises when bacteria evolve to survive the drugs, often because antibiotics are overused or misused (including being taken for viral illnesses); this is a major global health threat.
- The World Health Organization treats antimicrobial resistance as a serious threat, and patients are advised to complete the full prescribed course and avoid self-medication.
- Vaccines prevent infections, whereas antibiotics and antivirals treat them after they occur.
The bacteria-versus-virus targeting, penicillin and Fleming, the futility of antibiotics against viral colds, and antibiotic resistance are recurring public-health facts with field-medicine relevance.
Antibiotics do not work against viruses, so taking them for a cold or flu is useless and fuels resistance; only antivirals or vaccines address viral diseases. Resistance develops in the bacteria, not in the human body, and is worsened by misuse and incomplete courses.
Antibiotics kill bacteria (penicillin, Fleming 1928) and do nothing against viruses; antivirals target viruses; misuse of antibiotics breeds antimicrobial resistance.