Asymptomatic humans transmit dengue virus to mosquitoes

Abstract

Three-quarters of the estimated 390 million dengue virus (DENV) infections each year are clinically inapparent. People with inapparent dengue virus infections are generally considered dead-end hosts for transmission because they do not reach sufficiently high viremia levels to infect mosquitoes. Here, we show that, despite their lower average level of viremia, asymptomatic people can be infectious to mosquitoes. Moreover, at a given level of viremia, DENV-infected people with no detectable symptoms or before the onset of symptoms are significantly more infectious to mosquitoes than people with symptomatic infections. Because DENV viremic people without clinical symptoms may be exposed to more mosquitoes through their undisrupted daily routines than sick people and represent the bulk of DENV infections, our data indicate that they have the potential to contribute significantly more to virus transmission to mosquitoes than previously recognized.mosquito experimental infection | Cambodia | Aedes aegypti | human-to-mosquito transmission | dengue W ith 3.97 billion people living in 128 countries currently at risk for infection, dengue viruses (DENV-1 to -4) cause more human morbidity and mortality worldwide than any other arthropod-borne virus (1, 2). Aedes aegypti mosquitoes are the primary vectors of DENV throughout the tropics (3). Dengue prevention relies on the control of Ae. aegypti populations, which is failing in most parts of the world due to lack of resources, lack of political will, and/or ineffective implementation (4).Virus transmission from infected humans to mosquitoes is a critical step in dengue epidemiology, but due to logistical constraints it has been directly examined only in a handful of studies to date (5). In initial experimental infections of human volunteers during the 1920s (6, 7), the onset of clinical symptoms occurred 4-9 d after virus inoculation by mosquito bite (8). DENV-infected humans were infectious to mosquitoes from 2 d before to 2 d after the onset of symptoms, and Ae. aegypti fed on viremic people were able to transmit virus to another person after at least 11 d of extrinsic incubation (8). Results from later studies indicated that, for naturally infected people with clinically apparent dengue, the duration of detectable viremia was on average 4-5 d after the onset of symptoms, but could range from 2 to 12 d (9, 10). Investigators in Vietnam fed Ae. aegypti directly on 208 symptomatic, hospitalized dengue patients and reported that the probability of successful human-to-mosquito DENV transmission was coincident with the kinetics of viremia (11). Dengue patients were infectious up to 5 d after the onset of symptoms, which generally corresponded with "defervescence" (11).All previous studies on human-to-mosquito DENV transmission were limited to people with overt illness and did not consider subclinical infections. An estimated 300 million of the total 390 million DENV infections per year are clinically inapparent or mildly symptomatic, i.e., no illness that disrupted a person's ...

Invasiveness ofAedes aegyptiandAedes albopictusand Vectorial Capacity for Chikungunya Virus

“…For example, the ID 50 for DENV-1 and DENV-2 was lower than for DENV-3 and DENV-4 in one study in Vietnam [36], and field populations of A. aegypti demonstrated lower vector competence for the American genotype of DENV-2 than the Southeast Asian genotype [37]. It has been shown that people with asymptomatic and presymptomatic DENV infections had an approximately 100-fold lower ID 50 and resulted in larger viral loads in infected mosquitoes, which was interpreted as increased transmission potential [38].…”

Modelling the dynamics of Chikungunya in human and mosquito populations

“…and In (2), is the transmission probability of CHK and , , , > 1 are the modification parameters accounting for the assumption that infected humans and mosquitoes are more infectious than exposed humans and mosquitoes, respectively (Duong et al, 2015). Furthermore, is the per capita biting rate of female mosquito on the human host per unit time.…”

Back-to-the-future potential for autochthonous transmission of Aedes aegypti-transmitted viruses in eThekwini and urban coastal KwaZulu-Natal Province, South Africa

“…[62,63] Moreover, a 2015 study revealed that people with asymptomatic DENV infections can still infect biting mosquitoes. [64] Visitors or returning residents may infect blood-feeding Ae. aegypti without displaying signs of illness.…”