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Rapid active sampling quick, effective in measuring norovirus in rural Guatemala
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Two relatively rapid surveys effectively estimated the burden of childhood norovirus disease in a rural area of Guatemala, a study found.
Results of the rapid active sampling (RAS) surveys, as compared with relying on a smartphone application, were published in Open Forum Infectious Diseases.
“These findings support the utility of RAS surveys in estimating [norovirus] disease burden in resource-limited settings, allowing public health officials to quickly ascertain local prevalence data with limited public resources ... ” the study researchers wrote.
Their work included three groups of children between 6 weeks and 17 years of age. It spanned 25 communities in a 200-km2 area in coastal southwest Guatemala.
Parents were surveyed for symptoms in their children of acute gastroenteritis (AGE), which norovirus can cause. Each child also provided a fresh stool sample or rectal swab sample to test for norovirus.
The first cohort — the participatory syndromic surveillance (PSS) group — included 469 children from 207 households. Using a smartphone diary application, parents reported potential AGE symptoms like vomiting and diarrhea in children from April to September 2015.
Research staff followed up on reports of symptoms and collected stool samples. Households in the cohort made diary reports at a mean rate of 78%, and researchers conducted a prospective follow-up through June 2016.
Each of the RAS surveys, for which samples were collected with no follow-up, was conducted for 4 to 6 weeks. The study researchers noted that these types of surveys are administered more quickly than traditional active cohort surveillance and can be a viable alternative for countries with limited resources.
The first RAS survey was conducted in October and November 2015 and included 402 children. The second took place in January and February 2016 and included 368 children.
Norovirus and AGE were both present in 11% of PSS participants, and in 14% and 21% of those in RAS Surveys 1 and 2, respectively. Norovirus without AGE symptoms was present in 11% of children in the PSS cohort and in 12% and 8% of those in RAS Surveys 1 and 2, respectively.
For children providing available samples, the asymptomatic-to-symptomatic norovirus ratio was 6.3:1 for the PSS cohort, 3.3:1 for RAS Survey 1 and 3:1 for RAS Survey 2.
The PSS survey at the time of enrollment, along with both RAS surveys, “detected significantly greater incidence rates than the PSS prospective follow-up for both AGE ... and [norovirus with] AGE,” the researchers wrote.
The AGE incidence rate was 858/100 person-years (PY) for PSS at enrollment, 1,316/100 PY for RAS Survey 1, 697/100 PY for RAS Survey 2 and 11.4/100 PY for PSS follow-up (P < .001).
The rate of norovirus with AGE was 83/100 PY for PSS at enrollment, 154/100 PY for RAS Survey 1, 131/100 PY for RAS Survey 2 and 1.4/100 PY for PSS follow-up (P < .001).
The researchers concluded that the RAS method can be useful for more than just detecting norovirus.
“Future studies should replicate the use of RAS surveys in other settings and for other vaccine-preventable diseases,” they wrote, “as they offer a promising tool to measure changes in the burden of disease following the introduction of preventive interventions, such as [norovirus] vaccine.” – by Joe Green
Disclosure: Olson is partially supported by a grant from Takeda Vaccines Inc. Please see the full study for a complete list of all other authors’ relevant financial disclosures.
Perspective
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AGE surveillance systems as developed in this study appear to be useful for the epidemiologic study of norovirus infection in communities. Replication of this model in other settings may identify populations at high risk for norovirus infection and allow development of power calculations for planned norovirus vaccine studies. Noroviruses cause high rates of illness in all parts of the world, diagnostic techniques are not readily available and groups are developing vaccines that are reaching clinical field testing. The approach will not likely help in patient care because currently no successful therapy exists for norovirus gastroenteritis.
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