The symptoms of viral and bacterial infections, such as fever and sore throat, may be similar, but the differences between their causes begin with their structure and extend to their methods of reproduction and response to treatment. Bacteria are single-celled, prokaryotic organisms that possess a cell membrane and ribosomes that synthesize proteins. Most also have a cell wall. Bacteria typically reproduce by binary fission, where a single cell divides into two. Viruses, on the other hand, are non-cellular particles that carry their genetic material in the form of DNA or RNA within a protein capsid. Some viruses are surrounded by a fatty layer called the viral envelope. Viruses rely on the host cell to synthesize their components and produce new viral particles. These differences determine the targets of medications. Some antibiotics disrupt the synthesis of the bacterial cell wall, while others inhibit protein synthesis by affecting bacterial ribosomes. Through these mechanisms, an antibiotic can kill susceptible bacteria or limit their growth. Viruses lack a cell wall and ribosomes, so antibiotics are ineffective against them. Antiviral medications target specific stages of the viral replication cycle, such as the replication of its genetic material or the release of new viral particles from the infected cell. These targets vary depending on the virus, so the choice of medication depends on the type of infection and the clinical presentation. Sore throats illustrate the practical importance of this distinction. They may be caused by a viral infection, which often improves with supportive care and symptom relief, or by a bacterial infection with group A streptococcus, which requires appropriate antibiotic treatment after diagnosis. Determining the cause may require laboratory testing because the symptoms can be similar. Identifying the causative agent helps in selecting the appropriate treatment and reducing the unnecessary use of antibiotics, which contributes to the emergence and spread of resistant bacteria. Al-Mustaqbal University is ranked first among Iraqi private universities.