This article is more than 5 years old. Information may no longer be current.
‘Silent transmission’ fuels dengue epidemic
Click Here to Manage Email Alerts
A new study suggests that patients with asymptomatic dengue virus infection are 80% as infectious as symptomatic patients, underscoring the important role of “silent transmission” in spread of the disease, according to researchers.
The findings support recent blood-feeding experiments demonstrating that, despite previous theories, individuals with no “clinically apparent” symptoms are able to infect Aedes aegypti mosquitoes, according to Alex Perkins, PhD, Eck Family Assistant Professor of Biological Sciences at the University of Notre Dame, and colleagues.
“Until a few years ago, it was assumed that individuals with mild to no symptoms contributed relatively little to dengue virus transmission,” Perkins said in a press release. “Our research reveals that people showing no symptoms of dengue virus infection are contributing much more than was previously recognized, so that we now have a better idea of the large extent to which they contribute the spread of disease.”
WHO estimates that approximately 390 million people are infected with dengue virus worldwide each year. Of these individuals, only 96 million develop clinical manifestations. It was previously believed that asymptomatic patients were unable to drive transmission because their viremia levels were not high enough to “efficiently infect mosquitoes,” according to Perkins and colleagues. However, high seroconversion rates in areas with few reported cases and blood-feeding experiments contradicted this notion. Therefore, the researchers conducted a mathematical modeling study using within-host viral dynamics and human demographic data to determine the association between infectivity, disease severity and transmission in a hypothetical population.
The model revealed that, at the individual level, asymptomatic patients were approximately 80% (95% CI, 0-146) as infectious to mosquitoes as symptomatic patients. At the population level, 88% of all dengue virus infections were transmitted by mosquitoes that previously fed on an infected individual with no apparent signs or symptoms at the time of the bloodmeal. The model further estimated that 84% (95% CI, 82-86) of all infections were either linked to patients with no symptoms at any point during their infection or those with mild symptoms who may not seek treatment.
Among patients who do eventually develop symptoms, the model projected that 24% were bitten by mosquitoes during the pre-symptomatic phase of infection. Only 1.3% (95% CI, 1.1-1.4) of all infections were attributed to individuals whose infection was detected by surveillance systems.
The researchers concluded that their findings offer “valuable insights” that may have implications for current surveillance and infection control efforts.
“Unfortunately, based on our study, those who need to be targeted with intervention are either being identified after they have already contributed to transmission or are not being identified at all,” Perkins said in the release. “Our results indicate that it might be necessary to shift emphasis toward more proactive disease prevention strategies that do not rely as strongly on responding to detected cases.” – by Stephanie Viguers
Editors’ note: This story has been updated with the accurate percentage of net infectiousness among patients with asymptomatic infections. The editors regret this error.
Disclosures: Perkins reports receiving support from GlaxoSmithKline for unrelated work on dengue vaccine modeling. Please see the study for all other authors’ relevant financial disclosures.
Click Here to Manage Email Alerts