Patients were more likely to develop respiratory infections such as influenza after being exposed during a primary case visit—findings that may be applicable to the coronavirus as physicians open back up for in-person visits, according to a new study in Health Affairs.

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Study details

Using EHR and insurance claims data from athenahealth, researchers at athenahealth, Harvard University, and the University of Minnesota School of Public Health analyzed 105,462,600 primary care encounters that took place between 2016 and 2017 at 6,709 office-based primary care practices to identify visits where a person was exposed to a patient with an influenza-like illness.

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Specifically, researchers classified visits as "unexposed" if they occurred at least 90 minutes before the first visit of the day from a patient presenting with an influenza-like illness. In contrast, visits were classified as "exposed" if they were scheduled to start at the same time or after the office's first visit of the day from a patient with an influenza-like illness.

Researchers then compared unexposed and exposed visits to determine which patients were more likely to revisit the initial primary care practice with the flu within two weeks.

Findings

Within the study sample, 10,737,587 visits occurred on the same date as a visit from a patient with influenza-like illness at the same practice. Of those visits, 68.4% were categorized as "exposed" to a patient with an influenza-like illness.

Among all patients in the study, 2.7 per 1,000 patients returned to their initial practice within two weeks presenting with influenza. The researchers found that patients exposed to an influenza-like illness during their initial visit were 31.8% more likely to revisit with influenza within two weeks than patients who were not exposed—an increase that led to an additional 0.7 return visits per 1,000 visits, or approximately 5,140 additional influenza visits due to exposure.

In contrast, the researchers did not find similar patterns for urinary tract infections or back pain, both of which are noncontagious conditions.

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However, the authors also noted several limitations to the study. For example, they could track revisits only to the initial primary care practice and not urgent care centers or EDs, where patients may have otherwise sought care for their influenza symptoms. This likely led to an undercounting of actual influenza cases. The researchers also could not determine whether influenza transmission occurred in practices' waiting rooms or exam rooms.

The importance of infection control practices and telemedicine

"It's a widely accepted fact that patients can acquire infections in hospital settings, but we show that infection transmission can happen when you visit your doctor's office too," Hannah Neprash, an assistant professor at the University of Minnesota School of Public Health and the study's lead author, said. She also noted that the study is the first to document a relationship between influenza transmission and the timing of primary care visits among a national sample of adults.

According to Neprash and the other study authors, while the study findings may not be generalizable to coronavirus, they suggest that it could be transmitted to patients in primary care settings in a similar manner. "In-person outpatient care for influenza may promote nontrivial transmission of these viruses. This may be true for other endemic respiratory illnesses too, including Covid-19, but more research is needed," Neprash said.

Neprash said the study's findings "highlight the important of infection control practices and continued access to telemedicine services, as health care begins to return to pre-pandemic patterns."

In the study, the authors encourage clinics to implement "strict infection control practices" whenever a patient with influenza or a similar illness needs to be seen in person. Some suggested practices include mask wearing, hand washing, and separating sick patients into their own exam rooms.

The authors also suggest that telemedicine may be an important tool for infection control among patients with respiratory viruses, arguing that it should remain a financially viable option for providers as lawmakers debate how telemedicine will be reimbursed in the future. (Neprash et al., Health Affairs, 8/2021; University of Minnesota news release, 8/3)