Bacterial infections developed in about 5 percent of American adults hospitalized with firearm injuries, and the risk was concentrated among patients who needed surgery on the head, neck, spine, liver, or lower abdomen.
The finding comes from an analysis of 24,024 adults admitted to 323 hospitals nationwide, published as a research letter in JAMA Network Open. Researchers at the University of Maryland School of Medicine identified 1,236 patients, or 5.1 percent, who developed a bacterial infection. Most appeared during the initial hospitalization rather than after discharge.
Firearm injury has been studied extensively in terms of mortality. What happens to survivors during recovery has received far less attention, and infection is one of the complications that shapes how well and how quickly people recover.
Anatomy Drives the Risk Gradient
The location of injury and the type of surgery required mattered more than the injury's overall severity score. The median New Injury Severity Score in the cohort was consistent with minor injuries.
Patients undergoing procedures involving the head, neck, or spine carried the highest odds of early infection, more than five times that of other patients, with lower abdominal surgery also elevated. For late infection, liver surgery carried the highest odds at nearly four times, followed by head, neck, and spine procedures at more than double, according to CIDRAP.
At the other end, patients with handgun injuries and those undergoing surgery for extremity injuries showed the lowest early infection risk.
The anatomical pattern is clinically coherent. Injuries to the lower abdomen and bowel can allow intestinal contents to spill into the abdominal cavity, introducing gut bacteria into sterile spaces. Procedures on the head, neck, and spine involve tissue compartments where infection is difficult to clear and where hardware may be implanted. The most commonly identified organisms were Escherichia coli (20.9%), Staphylococcus aureus (12.4%), and enterococci (12.4%), a mix consistent with both gut- and skin-origin contamination.
Melike Harfouche, an associate professor of surgery at the school and a surgeon at the University of Maryland Medical Center, said the analysis identifies patients undergoing head, neck, or spine surgery as having "the highest risk of both early and late infections," per the University of Maryland School of Medicine.
Most Infections Show Up Before Discharge
Early infections diagnosed in hospital accounted for 4.3 percent of the cohort, while only 1.3 percent of patients developed an infection during the 90-day period following the initial hospitalization.
That timing has a practical implication. Infection risk after a firearm injury is concentrated in the window when patients are already under clinical observation, which is the setting where it is most likely to be caught. Late infections were the minority.
The study also found that bacterial infection was not independently associated with higher mortality among patients who survived at least one night in the hospital, with nearly identical proportions of infected and uninfected patients dying. That does not make infection harmless. Senior author Jonathan Baghdadi, an associate professor at the school, noted that although the study focused on mortality, infections can affect recovery in multiple ways, contributing to "long-term pain and disability."
The cohort was skewed young and male, with an average age at injury of 32.9 years and 85.3 percent men. Antibiotic therapy ran a median of one day across the cohort, and nine days among patients who developed an infection. The researchers noted that antibiotic exposure among patients who did not develop infections was generally low, which is consistent with current recommendations to limit preventive antibiotic use in many firearm injury cases.
Administrative Data Sets the Boundaries of the Finding
The analysis drew on the Premier Healthcare Database, covering admissions from January 2019 through May 2021. That source shapes what the study can and cannot say.
Administrative hospital data captures billing and coding records rather than detailed clinical narrative. A significant structural limitation is that follow-up encounters were assessed at the same hospital. A patient who developed an infection and sought care at a different facility would not be counted, meaning the 1.3 percent late infection figure is likely an undercount rather than a precise measure.
The study period also overlapped with the COVID-19 pandemic, which affected hospital operations, length of stay, and care-seeking behavior in ways not accounted for in this study.
These are observational findings. They describe which patients developed infections, not why, and they cannot establish that any specific surgical approach or antibiotic strategy caused or prevented them. The researchers describe this as the largest analysis of its kind, a statement about scale rather than certainty. Baghdadi has said he hopes the definition the team developed for identifying infection in administrative datasets will enable other researchers to pursue more specific clinical questions.
Signs That Warrant a Call After Discharge
For patients recovering from a firearm injury and the family members caring for them, the useful takeaway is knowing what to watch for and when to act.
Signs that should prompt contact with the surgical team include fever, increasing rather than decreasing pain at a wound or incision site, redness spreading outward from a wound, warmth, swelling, or drainage that is cloudy, discolored, or foul-smelling. A wound that had been improving and then began to worsen is a particularly meaningful change.
Symptoms suggesting a more serious problem, including high fever with shaking chills, confusion, rapid breathing, or a rapidly spreading area of redness, warrant urgent evaluation rather than a scheduled call.
Follow-up appointments matter more than they may seem to. Patients who miss post-discharge visits lose the window in which a developing infection is most easily addressed. Transportation, cost, and insurance gaps are real barriers here, and hospital social workers and trauma recovery programs can often help arrange follow-up care. Many trauma centers operate violence intervention programs that assist with both medical follow-up and practical needs during recovery.
Anyone prescribed antibiotics after discharge should complete the full course as directed and raise questions with a clinician rather than stopping early.
The broader context is that firearm injury research has concentrated heavily on mortality, and survivors have received comparatively little study. A far larger number of Americans are hospitalized and discharged than die, and what happens to that second group during recovery shapes long-term function, return to work, and ongoing pain. It remains thinly documented, as the study authors note.
Larger prospective studies that track patients across health systems would be needed to more accurately measure late infections.
Key Questions Answered
What did the study find? Among 24,024 adults hospitalized with firearm injuries, about 5 percent developed a bacterial infection, most during the initial hospitalization.
Which patients faced the highest risk? Those undergoing surgery involving the head, neck, spine, liver or lower abdomen. Extremity surgery and handgun injuries carried the lowest early risk.
Did infection increase the risk of death? Not independently, among patients who survived at least one night in the hospital. Infection was still associated with complications affecting recovery.
Which bacteria were most common? Escherichia coli, Staphylococcus aureus and enterococci.
What are the study's main limitations? It used administrative hospital data, and follow-up was tracked only at the same hospital, so late infections treated elsewhere were likely missed.
What symptoms should patients watch for after discharge? Fever, worsening pain, spreading redness, warmth, swelling, or cloudy or foul-smelling drainage from a wound.
When is urgent care needed? High fever with chills, confusion, rapid breathing, or rapidly spreading redness warrants immediate evaluation.
