We still dońt know who bleeds in Dengue. A systematic review of the literature

Background

Already, Dengue affects 400 million individuals every year. Its main drivers, urbanization, globalization, and climate change, however, will spread the disease even further and potentially threaten billions. In Dengue, bleeding occurs frequently. Severe bleeding strongly increases mortality and immediate medical response is crucial for survival. Predicting the occurrence and course of bleeding in advance would improve clinical outcome, reduce unnecessary hospitalization, and improve economic efficiency.

Methods

Following the PRISMA-guidelines, we conducted a systematic review of the literature to identify predictors of bleeding in acute confirmed Dengue. We searched Pubmed, Web of Science, IRIS, LILACS, and the Cochrane Archives and included all prospective longitudinal studies restricting neither language nor study sample characteristics.

Results

We included 19 studies but found that most data suffered from high risk of bias because of poor reporting and not accounting for confounding. Only five studies were more reliable, and they unanimously reported that age-, and platelet count predicted bleeding severity. The body of evidence was too weak to draw conclusions for the other 23 markers investigated. Crucially, the researchers had defined central concepts in fundamentally different ways and thus prevented the comparison of their findings.

Conclusions

Our systematic review of the literature showed that more research is needed to create a reliable prediction model for bleeding in Dengue. We have moderate certainty that platelet count- and age predict bleeding severity. Our study exposed the urgent need to improve the quality of research in Dengue epidemiology. Most importantly, our findings illustrate the necessity to harmonize central concepts within the Dengue research community. To tackle the challenge that Dengue is bound to become, we need dialogue across research groups and collaboration that overcomes the limited impact of individual studies.

Key messages

We know too little about predictors of bleeding in Dengue. Reliable data is needed to identify new markers and to confirm existing markers that are carried by a weak body of evidence. We urge investigators to collaborate. To overcome the limitations of individual studies, we need better comparability and a scientific dialogue based on common definitions of core concepts in Dengue.

[Imported viral infections in international travel; from the virtual to real epidemiology of pandemics]

Viruses have become more mobile alongside with increasing human mobility and speed of travel. At the same time we get access to information on viral outbreaks and epidemics from large parts of the world faster than ever before. Two recent epidemics will be presented to explore the value and the consequences of communicating epidemiological information through the Internet. The epidemiology, clinical features, diagnostic procedures and prophylaxis of imported viral infections are presented. Risk factors for the emergence and resurgence of viral diseases are being discussed.

Emerging viral pathogens in long-term expatriates (II): Dengue virus

Dengue virus infections have been well known for many years; still dengue virus is regarded as an 'emerging' pathogen, as the disease profile is changing. Its geographical range and overall incidence, and the incidence of the associated complications, dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS), are on the increase. Modern-day travel and increasing urbanization seem to be the main contributing factors. In order to estimate the risk of infection during long-term stays in dengue-endemic countries, we tested sera obtained from 323 development aid workers and their family members who had spent on average 9.8 years in dengue-endemic regions for the presence of dengue virus antibodies. Dengue virus antibody screening was done by a commercially available immunofluorescence test (IF). Reactive samples were re-tested by an in-house IF and also tested for cross-reactivity to yellow fever virus using yellow fever IF and neutralization test (NT). Evaluation of the results revealed that the screening test has a specificity of at least 63.2%. In 12 of 19 initially positive cases crossreacting antibodies against yellow fever virus could be ruled out. Three cases remained indeterminable, whereas four of the reactive and 10 (out of 12) of the borderline reactive cases showed crossreactivity with yellow fever virus, probably due to previous vaccination. We found seroprevalence rates of 4.3% with no significant differences related to gender or area of upbringing. Seroprevalence rates were evaluated according to region of suspected or confirmed infection. In two cases the dengue infection had taken a classical clinical course; in another three cases an extraordinary febrile illness was reported in the history. None of the other seropositive individuals had a history of an illness possibly attributable to dengue virus infection. Our results show that there definitely is a risk for long-term expatriates to acquire (mostly non- or oligo-symptomatic) dengue infection, which might be important especially in the light of the supposed aetiology of DHF or DSS as a secondary infection with another dengue virus serotype.

Emerging viral pathogens in long-term expatriates (I): Hepatitis E virus

Hepatitis E virus (HEV) is one of the so-called 'emerging' viral pathogens, whose role is increasingly being recognized. To estimate the risk of HEV infection during long-term stays in HEV-endemic countries, 500 serum samples obtained from development aid workers and their family members who had spent on average 9 years in HEV-endemic regions were tested for antibodies against HEV by ELISA and Immunoblot. We found seroprevalence rates of 5-6% with no significant differences related to gender or area of upbringing (raised in an HEV-endemic vs. nonendemic region). Seroprevalence rates did not increase with increasing number of stays or number of expatriate years. None of 77 children and adolescents tested was positive for anti-HEV. The Indian subcontinent showed the highest seropositive rate with 10%. In subjects returning from West and Central Africa, East Africa, South-east Asia and Latin America seroprevalence rates were around 7%. We found a comparatively low seroprevalence rate of 2.1% for the Arab countries and the Middle East. Our results show that there definitely is a risk for long-term expatriates to acquire HEV infection; however, in most of our cases infection seems to have been non- or oligo-symptomatic.