Epidemiological monitoring of the last outbreak of yellow fever in Brazil - An outlook from Portugal

Mechanisms of Yellow Fever Transmission: Gleaning the Overlooked Records of Importance and Identifying Problems, Puzzles, Serious Issues, Surprises and Research Questions

In viral disease research, few diseases can compete with yellow fever for the volume of literature, historical significance, richness of the topics and the amount of strong interest among both scientists and laypersons. While the major foci of viral disease research shifted to other more pressing new diseases in recent decades, many critically important basic tasks still remain unfinished for yellow fever. Some of the examples include the mechanisms of transmission, the process leading to outbreak occurrence, environmental factors, dispersal, and viral persistence in nature. In this review, these subjects are analyzed in depth, based on information not only in old but in modern literatures, to fill in blanks and to update the current understanding on these topics. As a result, many valuable facts, ideas, and other types of information that complement the present knowledge were discovered. Very serious questions about the validity of the arbovirus concept and some research practices were also identified. The characteristics of YFV and its pattern of transmission that make this virus unique among viruses transmitted by Ae. aegypti were also explored. Another emphasis was identification of research questions. The discovery of a few historical surprises was an unexpected benefit.

Mosquito-Borne Diseases Emergence/Resurgence and How to Effectively Control It Biologically

Deadly pathogens and parasites are transmitted by vectors and the mosquito is considered the most threatening vector in public health, transmitting these pathogens to humans and animals. We are currently witnessing the emergence/resurgence in new regions/populations of the most important mosquito-borne diseases, such as arboviruses and malaria. This resurgence may be the consequence of numerous complex parameters, but the major cause remains the mismanagement of insecticide use and the emergence of resistance. Biological control programmes have rendered promising results but several highly effective techniques, such as genetic manipulation, remain insufficiently considered as a control mechanism. Currently, new strategies based on attractive toxic sugar baits and new agents, such as Wolbachia and Asaia, are being intensively studied for potential use as alternatives to chemicals. Research into new insecticides, Insect Growth Regulators, and repellent compounds is pressing, and the improvement of biological strategies may provide key solutions to prevent outbreaks, decrease the danger to at-risk populations, and mitigate resistance.

Recent sylvatic yellow fever virus transmission in Brazil: the news from an old disease

Yellow fever (YF) is an acute viral disease, affecting humans and non-human primates (NHP), caused by the yellow fever virus (YFV). Despite the existence of a safe vaccine, YF continues to cause morbidity and mortality in thousands of people in Africa and South America. Since 2016, massive YF outbreaks have taken place in Brazil, reaching YF-free zones, causing thousands of deaths of humans and NHP. Here we reviewed the main epidemiological aspects, new clinical findings in humans, and issues regarding YFV infection in vectors and NHP in Brazil. The 2016-2019 YF epidemics have been considered the most significant outbreaks of the last 70 years in the country, and the number of human cases was 2.8 times higher than total cases in the previous 36 years. A new YFV lineage was associated with the recent outbreaks, with persistent circulation in Southeast Brazil until 2019. Due to the high number of infected patients, it was possible to evaluate severity and death predictors and new clinical features of YF. Haemagogus janthinomys and Haemagogus leucocelaenus were considered the primary vectors during the outbreaks, and no human case suggested the occurrence of the urban transmission cycle. YFV was detected in a variety of NHP specimens presenting viscerotropic disease, similar to that described experimentally. Further studies regarding NHP sensitivity to YFV, YF pathogenesis, and the duration of the immune response in NHP could contribute to YF surveillance, control, and future strategies for NHP conservation.

Imported Zika virus infections in Hungary between 2016 and 2018

Zika virus is a mosquito-borne flavivirus with significant public health concern due to its association with neurological symptoms and intrauterine malformations. Although it is endemic in tropical and subtropical areas, sexual transmission raises the possibility of autochthonous spreading elsewhere. We describe the first laboratory diagnosed imported Zika-infections of Hungary, to highlight the challenges of microbiological identification of the pathogen, caused by serological cross-reactivity and short viremia. Serological examination was carried out using indirect immunofluorescent assay and enzyme-linked immunosorbent assay. Plaque-reduction neutralization test was used for verification purposes. A wide range of clinical specimens: serum, whole-blood, urine, saliva, and semen were analyzed by molecular methods, and sequencing was applied in case of PCR positive results to identify the virus strain. Zika-infected patients with previous vaccination against flaviviruses or possible flavivirus infection in the past showed high serological cross-reactivity, and even cross-neutralizing antibodies were observed. Zika virus RNA could be detected in urine specimen in case of two patients, and in EDTA-anticoagulated whole-blood sample of one patient. The detected strains belong to the Asian lineage of the virus. We presume that serological investigation of imported Zika virus could be altered by infections, vaccination of endemic flaviviruses in Hungary and vice versa.

Kidney involvement in yellow fever: a review

Yellow fever is one of the most important mosquito-borne diseases, which still affects a significant number of people every year, mainly in tropical countries. Mortality can be high, even with intensive treatment due to multiple organ failure, including acute kidney injury (AKI). This disease can also be a burden on the health care system in developing countries, without mentioning the number of lives that could be spared with an early diagnosis and adequate monitoring and treatment. The pathophysiology of yellow fever-induced acute kidney injury (AKI) is still to be completely understood, and the best clinical approach has not yet been determined. This manuscript presents the most recent scientific evidence of kidney involvement in yellow fever, since AKI plays an important role in the mortality rate. Recent outbreaks have occurred in Brazil and further studies are required to provide a better clinical control for patients with yellow fever.

2018 in review: five hot topics in tropical medicine

The year 2018 heralded many new developments in the field of tropical medicine, including licensure of novel drugs for novel indications, licensure of existing drugs for existing indications but in novel settings, and globalized outbreaks of both vector-borne and zoonotic diseases. We herein describe five top stories in tropical medicine that occurred during 2018, and illuminate the practice-changing development within each story.