Measuring Effects of Flu, COVID Co-Infections

Investigators with St. Barnabas Hospital in the Bronx in New York City want to point out that theirs is a small study—comprising just 18 patients—and so therefore the ubiquitous caveat toward the end of every study that “more studies on this subject should be performed” carries a little more weight than usual.

And though it may be small, it is certainly timely. They wanted to find out if patients suffering from both coronavirus’ disease 2019 (COVID-19) and influenza have worse outcomes than patients suffering from COVID-19 alone.

“There was no difference in the outcome in COVID-19 patients co-infected with influenza compared to non co-infected patients, however, a larger sample of cases will be needed for further assessment of these outcomes,” concludes the study “Association Between Influenza Co-infection and Poor Outcomes in Patients Hospitalized with COVID-19,” which was unveiled at ID Week.

The study notes that there have not been that many reported incidents of people co-infected with COVID-19 and the flu. But…. “Both infections have been known to share similar mechanisms of transmission, however currently, there is no evidence regarding the relationship between co-infection between this viruses and worsening outcomes,” the study states. “Once social distancing measures are eased, and daily activities resumed, there is a possibility for a second wave of cases. Given the incidence of influenza is higher during winter, a higher co-infection rate is expected in these months.”

Infection preventionists and other healthcare professionals have been bracing for the double whammy of flu and COVID-19 for several months. Back in August, Linda Spaulding, RN, BC, CIC, CHEC, CHOP, a member of Infection Control Today®’s Editorial Advisory Board, told ICT® in a Q&A that this is uncharted territory; the healthcare system has never had to deal with SARS-CoV-2 and influenza at the same time. “Infection control people really have to monitor closely all respiratory viruses that are out there and be sure that you’re working actively with management to help put in place whatever needs to be put in place,” Spaulding said.

The St. Barnabas Hospital investigators in their hospital-based case-control study found 19 patients who’d been co-infected with the flu and COVID-19, but 1 of the patients did not meet the inclusion/exclusion criteria. Investigators reviewed the medical data on the remaining 18 patients.

“Controls were selected from the remaining pool of patients with COVID-19 in the same period. Cases were matched for age, sex and underlying comorbidities (hypertension, diabetes mellitus, liver disease, cardiovascular disease, HIV status, immunocompromised state other than HIV),” the study states. “The measured outcomes were: in-hospital mortality, need for mechanical ventilation, need for vasopressors and need for renal replacement therapy. For each outcome, Chi Square test and Odds ratio were obtained.”

Investigators stated concerns that the social distancing, hand hygiene and masking that’s been so crucial in attempts to slow COVID spread might be relaxed giving both COVID and influenza a chance to infect more people.

Kevin Kavanagh, MD, another member of ICT®’s Editorial Advisory Board, said in a Q&A back in August that those methods used against COVID seem to be particularly effective against the flu. The rates of flu in the Southern Hemisphere and in even back in March in the United States “just plummeted.”

“It’s a very steep slope,” Kavanagh said in August. “And so one would ask, ‘Why did that happen?’ Well, it happened because of the use of masks, hand hygiene, and social distancing. These same public health initiatives and strategies which are very effective on COVID-19 are even more effective with the flu.”

The St. Barnabas investigators found: “After statistical analysis, no significative difference was found in the following variables: in-hospital mortality [Odds ratio (OR) 0.769; 95% confidence interval (CI): 0.185-3.191; p value= 0.717], need for mechanical ventilation (OR 1.3; 95% CI: 0.313-5.393; p value= 0.717), need for vasopressors (OR 1.923; 95% CI: 0.383-9.646; p value= 0.423), need for renal replacement therapy (OR 1.0; 95% CI: 0.208-4.814; p value= 1.0).”

Nonetheless, flu and COVID co-infection remains a concern as winter approaches.