The global pandemic caused by the novel coronavirus SARS-CoV-2, which leads to Coronavirus Disease 2019 (COVID-19), presented a massive challenge to public health. People sought any possible treatment, leading to confusion about which medications were appropriate. A common question was whether antibiotics, used to treat many infections, could be effective against COVID-19. The answer is no, because COVID-19 is caused by a virus, and antibiotics are designed to target bacteria.
Understanding the Viral Nature of COVID-19
Viruses and bacteria, though both microscopic agents of disease, are fundamentally different biological entities. Bacteria are single-celled, free-living organisms that possess all the necessary machinery to survive and reproduce on their own. They are self-sufficient cells enclosed by a cell wall and membrane, containing their own genetic material and metabolic systems.
A virus, in contrast, is not considered a living organism; it is an acellular particle composed of genetic material (DNA or RNA) encased within a protein shell. Viruses lack the internal structures and metabolism required for independent reproduction. They are obligate intracellular parasites, meaning they must hijack a host cell, such as a human lung cell, to force it to produce new copies of the virus.
Why Antibiotics Cannot Treat Viral Infections
Antibiotics are a class of drugs specifically engineered to disrupt the life processes and structures unique to bacterial cells, which viruses do not possess. Many antibiotics, such as penicillin, work by targeting and interfering with the synthesis of the bacterial cell wall, which is largely made of peptidoglycan. Since human cells and viruses lack this specific cell wall structure, this mechanism has no effect on the virus or the human host.
Other antibiotics function by interfering with essential bacterial processes like protein synthesis or nucleic acid replication. They target the specific structure of the bacterial ribosome or unique bacterial enzymes. Viruses do not have their own ribosomes; instead, they commandeer the host cell’s ribosomes to create viral proteins. Because the molecular targets of antibiotics are absent in viral particles, the drugs cannot stop the SARS-CoV-2 virus from replicating.
The Role of Antibiotics in COVID-19 Management
Although antibiotics are ineffective against the SARS-CoV-2 virus itself, they were frequently prescribed to patients hospitalized with COVID-19. This practice is primarily due to the risk of a secondary bacterial infection, or co-infection, which can occur alongside or after the initial viral illness. A severe viral infection, such as COVID-19 pneumonia, weakens the body’s defenses and damages lung tissue, creating an opportunity for bacteria to invade.
In hospital settings, especially in intensive care units, patients may develop severe complications like ventilator-associated pneumonia, which is often bacterial. Since it is difficult to immediately distinguish a bacterial infection from a viral one based solely on clinical symptoms, doctors often use empirical antibiotic therapy. This means broad-spectrum antibiotics are administered as a precautionary measure until laboratory tests can confirm the presence of a bacterial infection.
Global data revealed that only 8% to 10% of hospitalized COVID-19 patients actually had a confirmed bacterial co-infection requiring antibiotics. However, up to three out of four hospitalized patients were treated with antibiotics, reflecting widespread overuse. When a bacterial infection is confirmed, the antibiotic treats the secondary condition, not the underlying COVID-19 viral infection.
Public Health Consequences of Misuse
The widespread, often unnecessary, use of antibiotics during the pandemic has contributed to the global crisis of antimicrobial resistance (AMR). AMR occurs when bacteria evolve and develop the ability to withstand the effects of previously effective antibiotics. This evolution is accelerated by overuse, as it provides a strong selective pressure for resistant bacterial strains to survive and multiply.
The Centers for Disease Control and Prevention (CDC) reported that resistant hospital-onset infections and associated deaths increased significantly during the first year of the pandemic. Pathogens such as carbapenem-resistant Acinetobacter baumannii and multidrug-resistant fungi like Candida auris saw substantial increases in reported cases. This rise in resistance means that common infections are becoming much harder to treat, potentially leading to increased mortality.
Using antibiotics when they are not needed also poses risks to the individual patient, including side effects like diarrhea and nausea. Unnecessary use of broad-spectrum antibiotics can disrupt the body’s natural microbiota, leading to secondary infections caused by other organisms, such as Clostridioides difficile. Antibiotics should only be used under a healthcare professional’s guidance for a confirmed or strongly suspected bacterial infection to protect both individual health and the effectiveness of these medications.