COVID-19 Basics

COVID-19 is a respiratory infection caused by SARS-CoV-2. The virus spreads mainly through infectious respiratory particles released into the air, including from people who have not developed symptoms. It enters susceptible cells by binding to ACE2, including on respiratory epithelial cells. Viral replication and the host inflammatory response can injure the airways and alveoli, producing cough and impaired gas exchange. When alveolar injury becomes diffuse, fluid and inflammatory debris interfere with oxygen movement across the alveolar-capillary membrane. The lungs become less compliant, and viral pneumonia can progress to acute respiratory distress syndrome (ARDS). That mechanism explains why oxygenation and respiratory trajectory matter more than fever alone when judging severity. A patient may report only fatigue and cough while oxygen saturation falls. Conversely, fever can occur without severe respiratory compromise. The nurse therefore links symptoms to respiratory function: work of breathing, respiratory rate, ability to speak, skin colour, mental status, oxygen saturation, and any new need for respiratory support. Illness ranges from asymptomatic infection to critical disease. Older age, pregnancy, immunocompromise, incomplete recommended vaccination, and chronic heart, lung, kidney, liver, or...