Virusinfektio

Virusinfektio is an infection caused by viruses that invade the cells of a host organism and use the cellular machinery to replicate. Viruses are obligate intracellular parasites and require living cells to reproduce. The resulting cellular damage and the host’s immune response together determine the clinical picture of the infection.

Transmission and pathogenesis occur through various routes. Viruses can enter the body via the respiratory tract, gastrointestinal tract, blood, skin, or mucous membranes, and spread through droplets, aerosols, direct contact, bodily fluids, or vectors such as mosquitoes. After entry, the virus targets specific cell types (tropism), hijacks cellular processes to replicate, and causes direct cytopathic effects or triggers inflammatory responses that contribute to symptoms.

Clinical presentation varies widely by virus and host factors. Common symptoms include fever, fatigue, cough or sore throat, nausea or vomiting, diarrhea, muscle aches, or skin rashes. Severe disease can involve the lungs, brain, liver, or heart and is more likely in the very young, older adults, and immunocompromised individuals.

Diagnosis generally relies on laboratory tests, such as polymerase chain reaction (PCR) to detect viral genetic material, antigen testing, or serology to detect antibodies. Sample types depend on the suspected virus and may include nasal or throat swabs, blood, stool, or cerebrospinal fluid.

Treatment is often supportive, including hydration and rest. Antiviral medications are available for a limited number of viruses (for example, influenza, herpesviruses, and HIV) and are most effective when started early. Prevention focuses on vaccination when available, hand hygiene, respiratory etiquette, infection control, and reducing exposure through safe practices and vector control. Public health surveillance helps monitor outbreaks and guide interventions.