Present and future arboviral threats.

Dengue is a spectrum of disease caused by four serotypes of the most prevalent arthropod-borne virus affecting humans today, and its incidence has increased dramatically in the past 50 years. Due in part to population growth and uncontrolled urbanization in tropical and subtropical countries, breeding sites for the mosquitoes that transmit dengue virus have proliferated, and successful vector control has proven problematic. Dengue viruses have evolved rapidly as they have spread worldwide, and genotypes associated with increased virulence have expanded from South and Southeast Asia into the Pacific and the Americas. This review explores the human, mosquito, and viral factors that contribute to the global spread and persistence of dengue, as well as the interaction between the three spheres, in the context of ecological and climate changes. What is known, as well as gaps in knowledge, is emphasized in light of future prospects for control and prevention of this pandemic disease.

/pdf/global-spread-and-persistence-of-dengue-4jert0rib2.pdf

Global spread and persistence of dengue.

The dramatic global expansion of Aedes albopictus in the last three decades has increased public health concern because it is a potential vector of numerous arthropod-borne viruses (arboviruses), including the most prevalent arboviral pathogen of humans, dengue virus (DENV). Ae. aegypti is considered the primary DENV vector and has repeatedly been incriminated as a driving force in dengue's worldwide emergence. What remains unresolved is the extent to which Ae. albopictus contributes to DENV transmission and whether an improved understanding of its vector status would enhance dengue surveillance and prevention. To assess the relative public health importance of Ae. albopictus for dengue, we carried out two complementary analyses. We reviewed its role in past dengue epidemics and compared its DENV vector competence with that of Ae. aegypti. Observations from “natural experiments” indicate that, despite seemingly favorable conditions, places where Ae. albopictus predominates over Ae. aegypti have never experienced a typical explosive dengue epidemic with severe cases of the disease. Results from a meta-analysis of experimental laboratory studies reveal that although Ae. albopictus is overall more susceptible to DENV midgut infection, rates of virus dissemination from the midgut to other tissues are significantly lower in Ae. albopictus than in Ae. aegypti. For both indices of vector competence, a few generations of mosquito colonization appear to result in a relative increase of Ae. albopictus susceptibility, which may have been a confounding factor in the literature. Our results lead to the conclusion that Ae. albopictus plays a relatively minor role compared to Ae. aegypti in DENV transmission, at least in part due to differences in host preferences and reduced vector competence. Recent examples of rapid arboviral adaptation to alternative mosquito vectors, however, call for cautious extrapolation of our conclusion. Vector status is a dynamic process that in the future could change in epidemiologically important ways.

/pdf/consequences-of-the-expanding-global-distribution-of-aedes-2dmnm7vamg.pdf

Consequences of the expanding global distribution of Aedes albopictus for dengue virus transmission.

The number of cases of severe dengue disease continues to grow in endemic areas of southeast Asia, Central and South America, and other subtropical regions. Children bear the greatest burden of disease, and the development of an effective vaccine remains a global public health priority. A tetravalent vaccine is urgently needed and must be effective against all four dengue virus serotypes, be cost-effective and provide long-term protection. In this Review we discuss the unique immunological concerns in dengue virus vaccine development and the current prospects for the development of an acceptable vaccine, a goal that is likely to be reached in the near future.

/pdf/prospects-for-a-dengue-virus-vaccine-54zhcfxely.pdf

Prospects for a dengue virus vaccine.

There has been growing interest in Europe in recent years in the establishment and spread of invasive mosquitoes, notably the incursion of Aedes albopictus through the international trade in used tires and lucky bamboo, with onward spread within Europe through ground transport. More recently, five other non-European aedine mosquito species have been found in Europe, and in some cases populations have established locally and are spreading. Concerns have been raised about the involvement of these mosquito species in transmission cycles of pathogens of public health importance, and these concerns were borne out following the outbreak of chikungunya fever in Italy in 2007, and subsequent autochthonous cases of dengue fever in France and Croatia in 2010. This article reviews current understanding of all exotic (five introduced invasive and one intercepted) aedine species in Europe, highlighting the known import pathways, biotic and abiotic constraints for establishment, control strategies, and public health significance, and encourages Europe-wide surveillance for invasive mosquitoes.

/pdf/a-review-of-the-invasive-mosquitoes-in-europe-ecology-public-5eve7oe4dw.pdf

A review of the invasive mosquitoes in Europe: ecology, public health risks, and control options.

Autochthonous dengue infections were last reported in Hawaii in 1944. In September 2001, the Hawaii Department of Health was notified of an unusual febrile illness in a resident with no travel history; dengue fever was confirmed. During the investigation, 1,644 persons with locally acquired denguelike illness were evaluated, and 122 (7%) laboratory-positive dengue infections were identified; dengue virus serotype 1 was isolated from 15 patients. No cases of dengue hemorrhagic fever or shock syndrome were reported. In 3 instances autochthonous infections were linked to a person who reported denguelike illness after travel to French Polynesia. Phylogenetic analyses showed the Hawaiian isolates were closely associated with contemporaneous isolates from Tahiti. Aedes albopictus was present in all communities surveyed on Oahu, Maui, Molokai, and Kauai; no Ae. aegypti were found. This outbreak underscores the importance of maintaining surveillance and control of potential disease vectors even in the absence of an imminent disease threat.

/pdf/dengue-fever-hawaii-2001-2002-3eq949p73r.pdf

Dengue fever, Hawaii, 2001-2002.

A community cluster of severe group A streptococcal skin infections occurred in Maui, Hawaii with 3 fatal cases of necrotizing fasciitis in 2002. emm types 1, 12, 58, 74, 85 and 109 were identified from 8 patients. emm types 74 and 109 have not been previously described in the United States according to the Centers for Disease Control and Prevention database. The identification of uncommon emm types suggested that group A streptococcal serotypes in Hawaii are different from those in the continental United States and can result in serious disease.

/pdf/characterization-of-a-community-cluster-of-group-a-474re6w07u.pdf

Characterization of a community cluster of group a streptococcal invasive disease in maui, hawaii

Background: Falls in the elderly represent a public health crisis. Effective prevention programs need to conduct economic analyses. The Move With Balance program showed a 65% reduction in falls in institutionalized elderly. Methods: We evaluated the return on investment (ROI) of Move With Balance. We calculated the ROI for 2 situations: first, using data from the current study (N = 27); second, extrapolating the data to an “intended” annual program (N = 45) where training costs can be spread over 6 years. Results: The program costs for the current study was $11,143. Based on an efficacy rate of 65%, we estimated that 13 falls were averted among the 21 participants in the treatment group. At a cost of $1440/fall, total averted cost of falls was $18,720. The ROI was 1.7:1 for a 10-week period. Program effects persisted for at least 6 months. Extrapolating the current program costs and fall rates to include classes for 45 people twice a year, the annual program costs would be $27,217. Total annual averted co...

An Economic Evaluation of Preventing Falls Using a New Exercise Program in Institutionalized Elderly.

Abstract Purpose of Review To highlight recent literature on airport COVID-19 testing studies among travelers at international borders and to identify factors that may contribute to bias. Recent Findings Literature search shows vastly different study designs and goals for airport COVID-19 screening programs, with positivity rates ranging from 0.1 to 100%. Goals included detecting the maximum cases with enforced isolation, determining an accurate positivity rate among travelers, investigating alternative diagnostics, and evaluating pre-travel programs. Participation rates are in the low (27–40%) to high ranges (72–100%). Summary The implementation strategy differs depending on the primary goal. If the goal is to ban new cases or perform active surveillance of new variants, then it is reasonable to consider mandatory airport testing, or voluntary testing with genome sequencing and isolation. If the goal is to determine an accurate positivity rate among travelers or effectiveness of pre-travel programs, then it is reasonable to consider an anonymous, voluntary testing program (without associated isolation) to minimize self-selection bias or distortion of travelers. 

/pdf/airport-covid-19-testing-of-travelers-an-island-destination-3eh3ulv6.pdf

Airport COVID-19 Testing of Travelers: An Island Destination Perspective

Angiostrongyliasis (Rat Lungworm disease) is an emerging parasitic disease caused by the ingestion of gastropods infected with the neurotropic nematode Angiostrongylus cantonensis. The reduction of crop infestation with infected slug carriers may vary widely by protection method. We explored the application of barriers with valve mechanisms, whereby selective directional forces caused a greater number of slugs to exit than enter the protected plot, leading to decreased slug population densities at a steady state. Using field data, we constructed predictive models to estimate slug population densities at a steady state in protected plots with (1) no valve effect, (2) a valve effect, (3) no valve effect with a single breach of the barrier, (4) a valve effect with a single breach of the barrier, (5) a valve effect with a constant breach of the barrier, and (6) a repelling effect. For all scenarios, plots protected using a barrier with a valve effect had consistently lower slug densities at a steady state. Our findings support the use of barriers with valve mechanisms under different conditions, and potentially in combination with other interventions to reduce the contamination of crops by slug carriers of A. cantonensis. Improving barriers extends beyond disease mitigation to economic and cultural impacts on the local farmer and consumer communities.

/pdf/barriers-with-valve-mechanisms-are-predicted-to-protect-32y2y13f.pdf

Kristin Mills

Papers

Dengue fever, Hawaii, 2001-2002.

Characterization of a community cluster of group a streptococcal invasive disease in maui, hawaii

An Economic Evaluation of Preventing Falls Using a New Exercise Program in Institutionalized Elderly.

Airport COVID-19 Testing of Travelers: An Island Destination Perspective

Barriers with Valve Mechanisms Are Predicted to Protect Crops from Slug Carriers of Rat Lungworm Disease