Covid vs. flu

The comparison between Covid and flu is useful, but it is not a like-for-like contest. Hospitalized patients with either infection are already at the severe end of illness, so these findings speak most directly to people sick enough to need inpatient care. That makes the signal clinically important, while also limiting how far it can be generalized to milder community cases.

The strongest takeaway is not that flu is harmless, but that Covid appears to remain more systemically disruptive. A respiratory infection can still have wider effects on blood vessels, immune function and other organs, which helps explain why outcome studies often find more readmissions and more post-acute complications after Covid. That pattern is plausible biologically, but the exact mechanisms can vary by variant, prior immunity, age and underlying health.

As with all observational comparisons, numbers depend on who gets hospitalized and when. Changes in testing, treatment, vaccination, circulation of variants and baseline immunity can shift the apparent gap between the two illnesses. So the most responsible reading is not a fixed ranking for every person, but an evidence-based reminder that Covid still carries a meaningful burden even in the post-emergency phase.

For readers, the practical implication is simple: both infections deserve prevention-minded habits. Staying current with vaccines, reducing exposure when transmission is high and seeking timely care for worsening symptoms matter for either virus. The main difference is that current evidence suggests Covid more often brings downstream health consequences beyond the lungs, which is why dismissing it as “just another cold” is not supported by the data.

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Covid deaths peaked at close to 26,000 a week in the US in January 2021. Thankfully, its grim toll has diminished significantly since then. But a year after the pandemic disease lost its emergency status, it continues to kill hundreds of people each week in the US and around the world. Mortality data for 2024 are still emerging and incomplete, but the numbers show deaths from Covid remain much higher than those from the flu, to which it’s often compared. Epidemiologist Ziyad Al-Aly began analyzing millions of patient electronic health records four years ago to understand Covid’s effects. I wrote last week about his latest study, published in the journal JAMA. It found that patients hospitalized from October 2023 to March 2024 for Covid had a 35% higher risk of dying within 30 days than those hospitalized for flu. Al-Aly, who was listed this month among TIME magazine’s 100 most influential people in health in 2024, did the same analysis the previous year and found that Covid posed a 60% higher mortality risk than flu during the 2022-2023 season. Although the death rate among Covid patients is declining — dropping to 5.7% in the latest period from 6% a year earlier — Al-Aly’s research underscores how much more damage the coronavirus can afflict on the body than flu. He and his colleagues at the clinical epidemiology center of the Veterans Affairs St Louis Health Care System in Missouri followed patients hospitalized for either disease for 18 months to compare their acute and long-term effects. Once again, they saw that Covid carried a higher risk of dying than flu. Not only that, Covid also resulted in a greater likelihood of being readmitted to the hospital and of developing complications across all organs except for the pulmonary system, regardless of vaccination status. The research showed that Covid was “multi systemic” in its effects, whereas flu mostly targeted the respiratory tract, Al-Aly told me. “Both produce long-term health effects, but the burden of long-term health effects of Covid is bigger than flu,” he said. Flu is far from benign. The US Centers for Disease Control and Prevention estimates that it resulted in 100,000-to-710,000 hospitalizations — and between 4,900 and 51,000 deaths in the US annually — since 2010. Even though our immunity to Covid is building, the continued evolution of new virus variants means we still need to take it seriously. It’s not just another type of “cold,” Al-Aly said. “I wish it were true,” he added, “but it is simply not borne out by the data.”