The flu is deadly, though the risk is far from equal for everyone. In the most recent U.S. data, influenza directly caused 6,512 deaths in a single year, a rate of about 1.9 deaths per 100,000 people. When you include pneumonia triggered by the flu, that number jumps to over 48,000. For most healthy adults, the flu is a miserable but survivable illness. For certain groups, it can turn fatal within days.
Who Faces the Highest Risk
Age is the single biggest factor. Adults 65 and older account for a disproportionate share of flu deaths, largely because the immune system weakens with age and chronic health conditions become more common. At the other end of the spectrum, children younger than 2 are at elevated risk, with the highest hospitalization and death rates among infants under 6 months old.
Underlying health conditions dramatically change the odds. During recent flu seasons, 9 out of 10 people hospitalized with the flu had at least one chronic condition. The list includes asthma, COPD, diabetes, heart disease, kidney disease, liver disease, sickle cell disease, and conditions that weaken the immune system like HIV or cancer treatment. People with a BMI of 40 or higher, those who’ve had a stroke, and pregnant women (up to two weeks after delivery) also face increased risk.
Racial and ethnic disparities show up clearly in the data. Non-Hispanic Black, Hispanic or Latino, and American Indian or Alaska Native individuals are hospitalized with the flu at higher rates, reflecting broader differences in access to care and rates of underlying conditions. People living in nursing homes and long-term care facilities are also especially vulnerable, given the combination of close quarters and frail health.
One detail that surprises many parents: among children who died of the flu in the 2024-25 season, 44% had no underlying medical condition at all. The flu can kill otherwise healthy kids, which is part of why pediatric flu deaths get so much public health attention.
How the Flu Actually Kills
The flu doesn’t usually kill by overwhelming the body with virus alone. It kills through a chain of complications, and the lungs are almost always where things go wrong first.
The most direct path is viral pneumonia. The flu virus itself can destroy the lining of the airways and fill the lungs with fluid and blood, creating a condition similar to acute respiratory distress syndrome. The tiny air sacs that exchange oxygen become swollen, inflamed, and lined with a stiff membrane that blocks normal breathing. In severe cases, this leads to organ failure.
More commonly, the flu opens the door for bacteria. As the virus damages the airway lining, it exposes binding sites where bacteria can latch on and invade. The most frequent culprits are bacteria that normally live harmlessly in the respiratory tract but become dangerous once the flu has weakened the body’s defenses. Staph infections, including antibiotic-resistant strains, are a particularly deadly form of secondary bacterial pneumonia.
In the most severe cases, the immune system itself becomes the problem. When the body detects the virus, it releases a flood of inflammatory signals to recruit immune cells. Sometimes this response spirals out of control, producing what’s known as a cytokine storm. The resulting inflammation damages the tiny blood vessels in the lungs, causes blood clotting problems, and can spread to other organs. This runaway immune response is one reason the flu occasionally kills young, otherwise healthy people whose immune systems mount an aggressive but poorly controlled fight.
The Heart Attack Connection
The flu’s danger extends well beyond the lungs. A study published in NEJM Evidence found that a flu diagnosis was linked to a sixfold increase in heart attack risk over the following week. The intense inflammation the virus triggers can destabilize fatty plaques inside arteries, making them more likely to rupture and block blood flow. For someone already living with heart disease, the flu can be the event that pushes things over the edge.
What Hospitalization Looks Like
Most people with the flu recover at home, but a significant number end up in the hospital. Data from a Veterans Affairs study tracking the 2022-23 flu season found that out of roughly 16,800 flu infections, about 2,660 required hospitalization and 123 resulted in death. That translates to about 1 in 6 diagnosed cases needing hospital care and roughly 1 in 22 hospitalized patients dying. These numbers come from a population that skews older and sicker than the general public, but they illustrate how quickly the flu can escalate once it’s serious enough to require admission.
How Much Vaccination Reduces the Risk
Flu vaccination doesn’t eliminate the risk of death, but it meaningfully lowers it. In seasons when the vaccine matched circulating strains well, standard-dose vaccination was associated with a 25% reduction in mortality compared to being unvaccinated. High-dose vaccines, designed for older adults, showed reductions ranging from 17% to 29% across multiple seasons, even in years when the match between the vaccine and the circulating virus was poor.
These numbers reflect protection among people who still caught the flu despite being vaccinated. In other words, even when the vaccine fails to prevent infection entirely, it appears to reduce the severity enough to lower the chance of dying. That partial protection is especially important for older adults and people with chronic conditions, where the margin between a rough illness and a fatal one can be narrow.
Why Healthy People Underestimate the Flu
For most people under 65 with no chronic conditions, the flu feels terrible for a week and then resolves. That lived experience makes it easy to dismiss the flu as a bad cold. But the virus is unpredictable in ways that colds are not. It can trigger pneumonia, an out-of-control immune response, or a heart attack in people who had no reason to expect a life-threatening illness. The 44% of pediatric deaths occurring in children with no prior health problems underscores this point: the flu is not uniformly dangerous, but it is consistently unpredictable.
Ranking as the 11th leading cause of death in the U.S. when combined with pneumonia, influenza sits alongside kidney disease and suicide in its annual toll. It kills fewer people than heart disease or cancer, but far more than most infectious diseases that receive comparable media attention.