Dynamics of the 2006/2007 dengue outbreak in Brazil

A previous mathematical model explaining dengue in Singapore predicted a reasonable outbreak of about 6500 cases for 2006 and a very mild outbreak with about 2000 cases for 2007. However, only 3051 cases were reported in 2006 while more than 7800 were reported in the first 44 weeks of 2007. We hypothesized that the combination of haze with other local sources of particulate matter had a significant impact on mosquito life expectancy, significantly increasing their mortality rate. To test the hypothesis a mathematical model based on the reproduction number of dengue fever and aimed at comparing the impact of several possible alternative control strategies was proposed. This model also aimed at contributing to the understanding of the causes of dengue resurgence in Singapore in the last decade. The model's simulation demonstrated that an increase in mosquito mortality in 2006 and either a reduction in mortality or an increase in the carrying capacity of mosquitoes in 2007 explained the patterned observed in Singapore. Based on the model's simulation we concluded that the fewer than expected number of dengue cases in Singapore in 2006 was caused by an increase in mosquito mortality due to the disproportionate haze affecting the country that year and that particularly favourable environmental conditions in 2007 propitiated mosquitoes with a lower mortality rate, which explains the greater than expected number of dengue cases in 2007. Whether our hypothesis is plausible or not should be debated further.

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“…We found values around 1 . 5, which is in accord with estimates from reports from other parts of the world [7][8][9][10].…”

Section: Discussionsupporting

confidence: 89%

A hypothesis for the 2007 dengue outbreak in Singapore

Massad

Coutinho

et al. 2009

Epidemiol. Infect.

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“…In the mathematical models for dengue proposed so far, transmission intensity was often expressed as mosquito density [32, 33] or as basic reproductive number ( R 0 ) [9, 34, 35]. In the present study, R 0 represents transmission intensity, since R 0 is proportional to vector abundance [3, 36, 37].…”

Section: Methodsmentioning

confidence: 99%

Simulations to compare efficacies of tetravalent dengue vaccines and mosquito vector control

Thavara

Tawatsin

Nagao³

2013

Epidemiol. Infect.

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SUMMARYInfection with dengue, the most prevalent mosquito-borne virus, manifests as dengue fever (DF) or the more fatal dengue haemorrhagic fever (DHF). DHF occurs mainly when an individual who has acquired antibodies to one serotype is inoculated with another serotype. It was reported that mosquito control may have increased the incidence of DF and DHF due to age-dependency in manifesting these illnesses or an immunological mechanism. Tetravalent dengue vaccine is currently being tested in clinical trials. However, seroconversions to all four serotypes were achieved only after three doses. Therefore, vaccines may predispose vaccinees to the risk of developing DHF in future infections. This study employed an individual-based computer simulation, to emulate mosquito control and vaccination, incorporating seroconversion rates reported from actual clinical trials. It was found that mosquito control alone would have increased incidence of DF and DHF in areas of high mosquito density. A vaccination programme with very high coverage, even with a vaccine of suboptimal seroconversion rates, attenuated possible surges in the incidence of DF and DHF which would have been caused by insufficient reduction in mosquito abundance. DHF cases attributable to vaccine-derived enhancement were fewer than DHF cases prevented by a vaccine with considerably high (although not perfect) seroconversion rates. These predictions may justify vaccination programmes, at least in areas of high mosquito abundance. In such areas, mosquito control programmes should be conducted only after the vaccination programme with a high coverage has been initiated.

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“…The results are usually used to calculate surveillance indices such as the House Index (percentage of houses with larvae and/or pupae, also: Premise Index), the Container Index (percentage of water-containers with larvae and/or pupae) or the Breteau Index (number of positive containers per 100 houses) (Silver 2008). However, these indices do not provide for a significant assessment of the number of adults that are actually produced and the associated dengue transmission risk (Coelho et al 2008, Focks 2003, Méndez et al 2006, Reiter et al 1991, Scott and Morrison 2002.…”

Section: Active Search For Immature Stagesmentioning

confidence: 99%

“…In general, these traditional indices are poorly related to the risk of dengue transmission (Coelho et al 2008, Focks 2003, Méndez et al 2006, Reiter et al 1991, Scott and Morrison 2002. More advanced assessments of immature stages therefore focus only on pupae, as their abundance is more closely linked to adult population size (Focks 2003).…”

Section: Introductionmentioning

confidence: 99%

Olfaction in vector-host interactions

Takken¹,

Knols²

2010

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Dynamics of the 2006/2007 dengue outbreak in Brazil

Cited by 49 publications

References 12 publications

A hypothesis for the 2007 dengue outbreak in Singapore

A hypothesis for the 2007 dengue outbreak in Singapore

Simulations to compare efficacies of tetravalent dengue vaccines and mosquito vector control

Olfaction in vector-host interactions

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