A decade of norovirus disease risk among older adults in upper-middle and high income countries: a systematic review

Abstract

Background: Noroviruses (NoVs) are the most common cause of acute gastroenteritis (AGE) causing both sporadic and outbreak-associated illness. Norovirus (NoV) infections occur across all ages but certain sub-groups are considered at increased risk due to heightened transmission and/or symptom severity. Older adults are potentially at high risk of NoV-associated illness due to frequent outbreaks in long-term care facilities (LTCFs) and severe health outcomes following infection. Elucidation of NoV risk among older adults will support prevention, treatment and control efforts.

Methods: We conducted a systematic literature review to summarize the published risk estimates of NoV-associated illness, hospitalization and death among individuals aged 65 years and older. A structured search using defined NoV and gastroenteritis (GE) terms was performed in the PubMed and EMBASE databases of human studies published between January 1, 2003 and May 16, 2013.

Results: We identified 39 studies from high income (HI) and upper-middle income (UMI) countries. Thirty-six percent of publications provided risk estimates based on laboratory-confirmed or epidemiologically-linked population-based surveillance data using molecular diagnostic methods. Over the study period, estimated annual NoV rates and extrapolated number of cases among older adults in HI and UMI countries were: 29-120/10,000 or 1.2-4.8 million NoV-associated illnesses; 18-54/10,000 or 723,000-2.2 million NoV-associated outpatient visits; 1-19/10,000 or 40,00-763,000 NoV-associated inpatient visits; 0.04-0.32/10,000 or 2000-13,000 NoV-associated deaths. NoV was responsible for approximately 10-20 % of GE hospitalizations and 10-15 % of all-cause GE deaths among older adults. Older adults experienced a heightened risk of nosocomial infections. Those in LTCFs experience frequent NoV outbreaks and the range in attack rates was 3-45 %, case hospitalization rates 0.5-6 % and case fatality rates 0.3-1.6 %.

Conclusions: Older adults are at increased risk of severe NoV-associated health outcomes. NoV-associated hospitalization rates were higher, more severe, resulted in longer stays and incurred greater costs than for younger patients. NoV-associated mortality rates were approximately 200 % higher among individuals 65 years and older compared to <5 years. The burden of NoV among older adults is expected to rise along with societal aging and increased need for institutionalized care. NoV prevention in older adults, including potential vaccination, may significantly impact risk of severe illness.

Fig. 1

Literature search summary

Fig. 2

Estimated annual incidence rate per 10,000 (extrapolated number) of norovirus-associated gastroenteritis cases in older adults living in high and upper-middle income countries^a. ^aPopulation based on 2013 World Bank estimate of 401,680,000 individuals aged ≥65 years in high (208,960,000) and upper-middle income (192,720,000) countries. ^bAnnual mortality rate estimates based on following sources: Hall et al. [51], Werber et al. [63], van Asten et al. [68]. ^cAnnual inpatient rate estimates based on following sources: Haustein et al. [69], Lopman et al. [70], van Asten et al. [68]. ^dAnnual outpatient rate estimates based on following sources: Gastanaduy et al. [45], Phillips et al. [42], van Asten et al. [68]. ^eAnnual case rate estimates based on following sources: Werber et al. [63], Bernard et al. [32]; if estimate accounts for incidence data published in de Wit et al. [94] which was published prior to the inclusion dates for this review, the upper incidence rate estimate would be 310 per 10,000 which corresponds to 12,452,080 estimated cases in high and upper middle income countries annually