Final answer:
Viral infections are diseases caused by viruses, microscopic entities that replicate inside living cells. Notable examples include COVID-19 and AIDS. They are distinct from other types of infections such as those caused by bacteria, fungi, or parasites.
Step-by-step explanation:
Viral infections are a type of infectious disease that is caused by viruses, which are microscopic pathogens that invade and replicate inside the living cells of an organism. Unlike bacterial infections, which can often be treated with antibiotics, viral infections require different management strategies, including vaccines and antiviral medications. Within the plethora of pathogens, viruses are unique in that they are not considered alive outside of a host cell and are inert particles consisting of genetic material (either DNA or RNA) enclosed in a protein coat.
Two well-known diseases caused by viruses are COVID-19 and AIDS. COVID-19, caused by the SARS-CoV-2 virus, has had a profound global impact, leading to widespread illness and significant societal disruptions. AIDS, caused by the Human Immunodeficiency Virus (HIV), undermines the immune system, leading to life-threatening infections and diseases. Both examples illustrate the severe consequences that viral infections can have on human health.
To clarify, viral infections (option 3) are distinct from infections caused by bacteria, fungi, or parasites. Viruses require a living host to replicate and can infect all types of organisms, from humans to plants and even bacteria—in the case of bacteriophages. Understanding the mechanisms of viral transmission and infection can aid in the development of preventative measures and treatments to combat these pathogens.