Final answer:
Influenza can escalate to deadly pneumonia through a severe immune response called a cytokine storm, leading to fluid accumulation in the lungs and secondary infections, with the elderly and immune-compromised being most at risk.
Step-by-step explanation:
Influenza, commonly known as the flu, can develop into pneumonia through a progression of symptoms and microbial action. Initially, flu viruses, particularly certain virulent strains, infect the respiratory system, leading to symptoms like coughing, fever, and body aches. In severe cases, especially in vulnerable populations, the immune response can cause a cytokine storm with excessive inflammation that results in rapid fluid buildup in the lungs (pulmonary edema), creating an environment conducive to pneumonia. This pneumonia can be caused by the initial viral infection or by secondary bacterial infections that take advantage of a weakened immune system. Ultimately, this can lead to decreased oxygen exchange, systemic infection (sepsis), organ failure, and potentially death.
Pneumonia is particularly dangerous for the very young, the elderly, and those with chronic conditions since their immune responses may be compromised, reducing their ability to fight off the pathogens. While the flu itself can resolve with rest and care, the transition to pneumonia requires immediate medical attention, as it is a leading cause of death among susceptible individuals.