Strong triage system helps manage dual outbreak of COVID-19, dengue

When dealing with a dual outbreak of dengue and the novel coronavirus disease (COVID-19), a strong triage system, including designated testing wards and diagnostic tests, can help minimize the risk of healthcare-associated transmission, according to a new Singapore study.

From January to May 2020, the Singapore General Hospital screened 11,086 admissions for COVID-19. Of these, only 8.5 percent also underwent dengue serology testing, as ordered by the physician, due to matching clinical profiles. Only 868 patients (7.8 percent) eventually tested positive for COVID-19. [Am Trop Med Hyg 2020;doi:10.4269/ajtmh.20-0703]

Dengue was the main differential diagnosis in only 2.0 percent of patients initially admitted due to suspected COVID-19. Of the 868 confirmed COVID-19 cases, 8.1 percent (n=70) were also tested for dengue serology, and nine patients were positive for COVID-19 and potentially infected with dengue. Removing all false positives, only one patient was co-infected with COVID-19 and dengue.

“[I]t appears that in practice, the potential overlap in clinical syndromes is not large, even in a dengue-endemic area. Although our institution had to contend with the emergence of a COVID-19 pandemic during a dengue epidemic season, primary physicians were only compelled to rule out dengue in less than one-tenth of patients with confirmed COVID-19 infection,” the researchers said.

“However, our institution’s experience also demonstrates that when grappling with a COVID-19 pandemic during a dengue epidemic season, a triage strategy is necessary to detect cases of COVID-19 that may potentially be misdiagnosed as dengue,” they added.

Starting in February 2020, to improve the containment of COVID-19 amid a dengue outbreak, the Singapore General Hospital moved to admit all patients with undifferentiated symptoms of early viral infections to their respiratory surveillance ward (RSW) even if there had been no documented epidemiologic risk for COVID-19.

The RSW saw 1,751 patients from April to May 2020, of whom only 15 were eventually diagnosed with COVID-19. Two of those patients had false-positive dengue immunoglobulin M test results.

“Our institution’s policy of screening patients presenting with viral prodromes and nursing such patients in a designated RSW with decreased bed density and full personal protective equipment enabled the containment of these two patients in our institution’s RSW and mitigated potential exposure,” the researchers said, pointing out that none of 21 healthcare workers who came into close contact with these two patients showed evidence of onward transmission.

While a strict and efficient triage algorithm to differentiate dengue and COVID-19 is indispensable in areas with overlapping epidemics, the researchers acknowledged that this strategy may be difficult to replicate universally. It requires high levels of investment and support to be able to deliver COVID-19 test results quickly to ensure that the surveillance wards do not clog up.

“In resource-poor settings with limited access to supportive diagnostic tools, differentiating between these infections based on clinical signs and symptoms alone would certainly be more challenging,” they said.