Norovirus gastroenteritis is responsible for approximately $60 billion in costs worldwide, the majority of which result from illness-related productivity losses, according to data recently published in PLoS One.
These findings are supported by additional incidence analyses reported alongside the cost burden analysis, which suggest substantial rates of norovirus illness primarily affecting young children.
“You only seem to hear about it when people get sick on a cruise ship or at a restaurant, but norovirus is everywhere,” Sarah M. Bartsch, MPH, researcher at the Bloomberg School of Public Health at Johns Hopkins, said in a press release. “If we don’t focus on norovirus and teach people how to prevent it, little headway will be made to combat it.”
Costs driven by lost productivity
Despite data noting the significant and variable burden of norovirus gastroenteritis among high-, middle- and low-income countries, there are no systematic international assessments of norovirus’ cost to health care and society, Bartsch and colleagues wrote. To address this, the researchers constructed a computational simulation model capable of estimating economic burden by age, country income and cost-type. Global and regional incidence data were collected from the Foodborne Disease Epidemiology Reference Group, and used to calculate overall disease burden within four stratified age groups. A country’s economic standing was determined using gross national income per capita data from the World Bank and United Nations, or interpolated using data from similar countries in the region. When determining costs, the model assumed everyone with the illness accrued lost productive days, sought medical care at previously reported frequencies and, if applicable, obtained hospitalization at rates similar to those observed within the U.S. Additional simulations modifying key parameters — such as hospitalization probability or missed productivity days within age and national income groups — also were conducted.
Approximately 699 million norovirus illnesses (95% uncertainty interval, 489 million-1,086 million] and 219,000 deaths (95% UI, 171,000-277,000) were estimated to occur each year across all age groups, the researchers wrote. While these amounts led to a median $4.2 billion (95% UI, 3.2-5.7 billion) in direct health care costs, the addition of lost productivity resulted in an overall societal cost of $60.3 billion (95% UI, 44.4-83.4 billion). The majority of this was attributed to infections among children aged younger than 5 years, who represented $39.8 billion of the annual burden. High-income countries were responsible for 62% of global health system costs, despite similar disease incidence among low-, medium- and high-income nations.
These data indicate a significant loss in productivity that could go unnoticed during investigations primarily focused on mortality, the researchers wrote, and illustrate the potential benefit of increasing international focus on the gastrointestinal infection.
“The costs associated with norovirus are high — higher than for many diseases, including rotavirus, that have gotten a lot more attention,” Bruce Y. Lee, MD, MBA, associate professor in the international health department at Bloomberg School, said in the press release. “Our study presents an economic argument for greater consideration of norovirus. It has been flying under the radar for too long.”
High norovirus burden among children
Additional incidence and epidemiology data published alongside the cost analysis further characterized the burden of norovirus among various populations.
In a literature review of African norovirus studies, Janet Mans, PhD, senior lecturer at the University of Pretoria, South Africa, and colleagues analyzed findings from 19 studies conducted in 14 African countries. These studies — primarily focused on children seeking medical care— were used to form an estimate of the overall prevalence and distribution of norovirus genotypes within the continent, and revealed a 13.5% (95% CI, 12.7-14.3) rate of norovirus among those presenting with gastroenteritis. Studies reporting data on asymptomatic controls suggested an overall prevalence of 9.7% (95% CI, 8.4-11.1). Reported norovirus prevalence rates also were higher among studies that limited analysis to children aged 2 years or younger than in those including children aged 5 years or younger (18% vs. 11.8%; P < .001). Mans and colleagues also noted “remarkable” genotype diversity among each study, but wrote that many gaps remain in the characterization of adult cases.
Norovirus appears to significantly impact U.S. patients as well. In an analysis of 1,099 acute gastroenteritis specimens collected within the Kaiser Permanente health care network, Scott P. Grytdal, MPH, surveillance epidemiologist at the CDC, and colleagues found noroviruses to be the most commonly identified viral pathogen among all age groups (6%) as well as among children aged younger than 5 years (12%). The prevalence of norovirus-positive stools was greatest between November and March, they wrote, while the overall incidence of norovirus-associated outpatient visits and community disease were estimated to be 5.6 per 1,000 person-years and 69.5 per 1,000 person-years, respectively.
“A very high proportion of norovirus-positive specimens were genogroup GII, as expected form earlier reports,” Grytdal and colleagues wrote. “Our demonstrated burden of norovirus [acute gastroenteritis] in the community and outpatient settings justifies the effort to develop possible norovirus vaccines.”
Greater rates of norovirus-associated medical encounters were reported to occur among active duty U.S. military personnel and their beneficiaries. An analysis of medical records collected by the Armed Forces Health Surveillance Center from 1998 to 2011 by Brian Rha, MD, MSPH, medical officer at the CDC, and colleagues estimated norovirus to be the source of 31% and 27% of all-cause gastroenteritis medical encounters among active duty personnel and their dependents, respectively. These findings were driven by annual mean medical encounter rates of 292 (95% CI, 258-326) visits per 10,000 active duty personnel and 93 (95% CI, 80-105) visits per 10,000 dependents, which the researchers noted were substantially higher than previous estimates of the general population. Rates increased further among younger beneficiaries, with those younger than 5 years demonstrating a median annual rate of 435 encounters per 10,000 children. Although Rha and colleagues warned rates among these populations could be inflated by the free, high-quality health care available to many military members and their families, they wrote that the findings also may represent an increased exposure to diseases facilitated by close quarters and shared common spaces inherent to military lifestyles.
“While the full impact of norovirus disease on the U.S. military is still to be quantified, our results highlight the importance of norovirus as a cause of infectious gastroenteritis among active duty military personnel and their beneficiaries in nondeployment settings,” Rha and colleagues wrote. “Risk factor studies among [active duty] and [dependent beneficiaries] could improve our understanding of the epidemiology of norovirus and elucidate why rates are apparently higher in these populations.” – by Dave Muoio
Bartsch SM, et al. PLoS One. 2016;doi:10.1371/journal.pone.0151219.
Grytdal SP, et al. PLoS One. 2016;doi:10.1371/journal.pone.0148395.
Mans J, et al. PLoS One. 2016;doi:10.1371/journal.pone.0146280.
Rha B, et al. PLoS One. 2016;doi:10.1371/journal.pone.0148505.
Disclosure: The researchers report no relevant financial disclosures.