Studies Highlight Worldwide Economic Burden of Norovirus Gastroenteritis

Each year, norovirus infection is responsible for an estimated 684 million episodes of diarrhea and 212,000 deaths worldwide, and results in approximately $4.2 billion in healthcare costs and $60.3 billion in societal costs, a new report has highlighted.

Benjamin A. Lopman, PhD, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, and colleagues shared the results of their report in PLOS Medicine.

“Two-thirds of that burden is a result of disease in children under the age of five years. Low-, middle-, and high-income countries all have a considerable economic burden, indicating that norovirus gastroenteritis is a truly global economic problem,” the authors write.

Norovirus infection is the most common cause of gastroenteritis outbreaks worldwide, and the most common cause of foodborne disease in the United States. However, despite the increase in norovirus-related research in the last decade, as well as the availability of vaccines for norovirus that are recommended by the World Health Organization, progress in controlling the virus has remained slow. As a consequence, the CDC and the Bill and Melinda Gates Foundation assembled an expert group to examine the evidence for the global burden of norovirus and to consider how to address key gaps in the knowledge base about noroviruses—“with the ultimate goal of guiding the development of a norovirus vaccine for the populations that stand to benefit most: children in the developing world”.

In the article, the authors discuss data from some of the most recent norovirus studies. They stress that, so far, two main barriers have hindered norovirus control. One is the ubiquitous nature of norovirus gastroenteritis, and the second is because the virus is difficult to grow in cell culture in the laboratory—a key step in the development of diagnostic assays and vaccines against the virus. Indeed, the first demonstration of in vitro cell culture of norovirus was reported just 2 years ago, in 2014.

Dr. Lopman and colleagues emphasize some of the current data on the epidemiology and burden of norovirus disease in Africa, the United States, and military personnel—demonstrating just how common the virus is, even as it affects these diverse groups.

They note that, in African countries, norovirus is associated with 13.5% of diarrheal outbreaks in children. In addition, the incidence rate of norovirus disease in Kenya is approximately double that of the estimated rate in developed nations such as the United States, United Kingdom, and the Netherlands. Key information about norovirus in Africa is therefore lacking and is a critical knowledge gap.

The authors discuss regional epidemiologic patterns in the United States, including data from one study that estimated norovirus gastroenteritis incidence in the community at 6% per year, with much higher rates among children under 5 years. Another US study showed considerably higher estimates of norovirus gastroenteritis incidence among United States military personnel and their families, than among civilians in the population.

They also highlight another key challenge in developing a vaccine against norovirus—genetic diversity among circulating noroviruses. Nevertheless, studies have shown that genotype II type 4 (GII.4) strains predominate worldwide, with new GII.4 strains replacing each other every 2 to 4 years. Recent research has also improved understanding of immunity to norovirus, leading to breakthroughs that may therefore enhance vaccine development.

According to the authors, in order to offer substantial impact worldwide, future directions for norovirus control should involve vaccine development focusing on children in low-income settings. They also suggest that vaccine trials can be used to better characterize the disease burden and also to identify correlates of protection.

“Addressing these key issues will be vital to accelerate and achieve the development and implementation of interventions such as vaccines to control and prevent the tremendous global morbidity and mortality from norovirus,” the authors conclude.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.