viruses

Viruses are tiny infectious particles that can make us sick, but they can only multiply inside the living cells of a host (like humans, animals, or plants).

• A virus is much smaller than bacteria and is basically genetic material (DNA or RNA) wrapped in a protein coat. Some also have an outer fatty covering.
• Viruses are called obligate parasites because they cannot reproduce on their own; they “hijack” a cell’s machinery to make many new viruses.
• Once inside the body, viruses can damage or kill cells, and the body’s immune system reacts—this reaction causes many symptoms like fever, tiredness, and inflammation.
• Examples of viral diseases include flu, chickenpox, dengue, and COVID-19. Different viruses attack different parts of the body (like the lungs, skin, or blood).
• Antibiotics do not work against viruses because antibiotics target features of bacteria that viruses do not have. Viral infections are prevented mainly by vaccines, hygiene, and sometimes treated with special antiviral medicines.
• Viruses can spread in different ways—through air droplets (cough/sneeze), contaminated food or water, blood/body fluids, or via vectors like mosquitoes (for example, dengue).

Thinking of a virus as a “code in a protective shell” helps: it needs to enter a living cell to run that code and make more copies.