Study suggests Covid-19 mitigation measures may have reduced conjunctivitis incidence

Infection control measures put in place to prevent SARS-CoV-2 infection early in the Covid-19 pandemic may be responsible for a decline in the incidence of the highly contagious and common eye condition infectious conjunctivitis.

At a single academic center emergency department, visits for “pink eye” declined by 37% during the pandemic compared to pre-pandemic levels, while ED visits for common non-infectious eye conditions remained stable.

Online searches for “conjunctivitis” also declined by approximately 34% after April 2020, compared to prior pandemic search levels.

Writing in the journal JAMA Ophthalmology, researcher Aaron Lee, MD, of the University of Washington, Seattle, and colleagues, noted that the decline in internet searches occurred starting roughly two to three weeks after social distancing measures, shutdowns, and other Covid-19 mitigation strategies were put in place.

“This time lag may suggest that the decrease in the incidence of conjunctivitis cases in this study were from viral causes, adenovirus in particular,” they wrote. “The incubation period for adenovirus conjunctivitis is typically thought to be 5 to 12 days, although certain types of adenovirus have incubation periods of more than 2 weeks.”

They noted that pink eye accounts for 1% to 2% of primary care visits in the U.S.

“Acute viral conjunctivitis is transmitted through close personal contact, fomites, droplets in the air, and poor hand hygiene,” Lee and colleagues wrote, adding that “despite infection control programs and measures, acute viral conjunctivitis continues to be a public health concern and a substantial economic burden.”

The researchers hypothesized that social distancing and other Covid-19-related public health measures reduced infectious conjunctivitis incidence beginning early in the Covid-19 pandemic, and they used causal inference Bayesian modeling “to evaluate the potential association of the Covid-19 pandemic with infectious conjunctivitis in the U.S.”

Internet search data and emergency department data from the University of Washington, Seattle, were used in this study, and smartphone mobility data were temporally aligned to quantify social distancing.

The researchers reviewed hospital data on all patients who presented to the University of Washington emergency department from February 2015 to February 2021.

“Data were compared from before and after April 2020, when the CDC recommended members of the public wear masks, stay at least 6 feet from others who did not reside in the same home, avoid crowds, and quarantine if experiencing flu-like symptoms or exposure to persons with Covid-19 symptoms,” the researchers wrote.

A total of 1,156 emergency department visits with a diagnosis of conjunctivitis were recorded from January 2015 to February 2021.

Emergency department visits for nonallergic conjunctivitis decreased by 37.3% (95% CI, −12.9% to −60.6%; P<0.001), after April of 2020, while visits for corneal abrasion and posterior vitreous detachments remained relatively stable after adjusting for total emergency department encounters.

Search interest in conjunctivitis decreased by 34.2% (95% CI, −30.6% to −37.6%; P0<.001) after April of 2020.

Study limitations cited by the researchers included the lack of information on why ED visits declined during the Covid-19 lock down period.

They noted that “it is possible patients were less likely to go to the ED because of a fear of contracting Covid-19,” and they further noted that Covid-19 itself “may cause a confounding effect.”

“Infection with Covid-19 has been associated with conjunctivitis-like symptoms in 6.6% to 31.6% of patients. It is possible that this may be under reported because of the reduction of eye care during the pandemic as well as emphasis on more life-threatening clinical signs and symptoms of Covid-19,” they wrote.

In an accompanying commentary, ophthalmologist and epidemiologist Alfred Sommer, MD, of Johns Hopkins University, wrote that the novel use of internet search data in the study, which showed significant declines in searches for pink eye during Covid-19 lock down, “illustrates untapped uses lurking in the innovative interrogation of data contained in the World Wide Web.”

“I’d be surprised if this is not the first of many such correlations that will be sought, and refined, in the future, and become a valuable means of gaining insights that have until now eluded us about both infectious and non-infectious diseases, and their many characteristics,” Sommer wrote. “While there is no way of knowing which aspects of the Covid-19 interventions were most responsible for the seeming interruption in the spread of adenoviral conjunctivitis (masking, social distancing, excessive hand washing), this is an early glimpse of where ’armchair’ epidemiology will one day lead us.”

  1. Infection control measures put in place to prevent SARS-CoV-2 infection early in the Covid-19 pandemic appear to be responsible for a decline in the incidence of the highly contagious and common eye condition known as pink eye.

  2. Online searches for “conjunctivitis” declined by approximately 34% after April of 2020, compared to search levels prior to the pandemic.

Salynn Boyles, Contributing Writer, BreakingMED™

Funding was provided by the National Institutes of Ageing and the National Eye Institute.

Lavista Ferres is an employee of Microsoft Corporation. Coauthor Aaron Lee reported receiving grants from Santen, Regeneron, Carl Zeiss Meditec, the National Eye Institute, and Novartis and personal fees from Genentech/Roche, Johnson & Johnson, the FDA, Topcon, and Verana Health, outside of the submitted work, plus nonfinancial support from Microsoft during the conduct of the study and nonfinancial support from NVIDIA outside the submitted work.

Cat ID: 240

Topic ID: 92,240,730,933,190,926,192,927,151,928,925,934,240