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Cholera linked to drinking iced tea in Vietnam
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The chances of infection from cholera were heightened for the people of Ben Tre, Vietnam, when they drank iced tea, according to a study published in PLoS Neglected Tropical Diseases.
“Prior to implementation of control measures, Vietnam suffered a disproportionate burden of cholera,” Thuong V. Nguyen, MD, PhD, DTM&H, a senior medical epidemiologist at the Pasteur Institute in Ho Chi Minh City, Vietnam, and colleagues wrote. “[A vaccination program], in conjunction with improved personal hygiene and access to potable drinking water associated with both health promotion programs and economic growth, led to a substantial drop in the number of notified cholera cases. However, these gains have not been sustained.”
Nguyen and colleagues conducted a matched case-control study in the midst of an outbreak in the southern province Ben Tre, analyzing potential risk factors associated with cholera infection.
Between May 9 and Aug. 3, 2010, 60 patients with diarrhea and confirmed cholera infection were matched in a 1:4 ratio with controls based on commune, sex and age. The researchers took environmental samples from the case-patients’ villages to identify the sources of contamination.
Most of the risk factors the researchers identified during the outbreak were consistent with those found in previous studies, they said. For example, not always boiling drinking water (adjusted OR = 2.62; 95% CI, 1.03-6.67), having the primary water source located near a toilet (aOR = 4.36; 95% CI, 1.37-13.88), and living with someone who had acute diarrhea (aOR = 13.72; 95% CI, 2.77-67.97) were all risk factors for developing the infection.
However, results of their study also revealed that drinking iced tea may have contributed to the outbreak. Compared with just 3% of controls, 22% of case-patients drank iced tea within 1 week before illness onset (P < .001), with an adjusted OR of 8.40 (95% CI, 1.84-39.25).
“We know of no previous studies that have reported increased risk of infection specifically associated with iced tea consumption,” they wrote.
The researchers suspected that the ice used in the tea, which is purchased from street vendors rather than prepared at home, may have been contaminated and therefore contributed to the increased risk for infection. However, they were unable to obtain commercial and household ice to test for the presence of Vibrio cholerae.
They also observed “substantial cholera risk reductions in some subpopulations,” including people who drank stored rain water (aOR = 0.17; 95% CI, 0.04-0.63) and ate cooked seafood (aOR = 0.27; 95% CI, 0.10-0.73) and steamed vegetables (aOR = 0.22; 95% CI, 0.07-0.70).
Nguyen and colleagues said they found V. cholerae O1 Ogawa carrying ctxA in two of 25 river water samples and in one of six wastewater samples.
The researchers called for future microbiological and epidemiological investigations of cholera in commercial ice in Vietnam.
“This present study has important implications for Vietnam’s cholera responses,” they wrote. “Along with traditional approaches that focus on enhancement of safe water, sanitation and food safety, combined with periodic provision of oral cholera vaccines, a water quality monitoring system at ice-making plants should be established.” – by Katherine Bortz
- Reference:
- Nguyen TV, et al. PLoS Negl Trop Dis. 2017. doi:10.1371/journal.pntd.0005490.
Disclosure: The researchers report no relevant financial disclosures.