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Friday, November 10, 2017

Ongoing surveillance and vaccination are key to prevent yellow fever outbreak in humans

November 6, 2017
A combination of continuous monitoring of mosquitoes and non-human primate deaths, along with laboratory tests and increased vaccination, is crucial to prevent human cases of yellow fever in places where the virus is transmitted. Findings from a brief research report are published in Annals of Internal Medicine.
Yellow fever is a virus found in South America and Africa that is transmitted by . Transmission typically occurs in wild animals, but occasionally spills over to humans entering forest regions. Still, urban transmission is rare, mainly due to vaccination. Recently, concerns about reemergence of urban yellow fever have grown because of the reappearance and rapid spread of A aegypti (a type of mosquito that may carry yellow fever) in the urban environment. Further, immunization coverage for yellow fever is insufficient because it is usually administered to high-risk populations.
Researchers from the Instituto Goncalo Moniz studied the 2017 epizootic outbreak (outbreak within animals) of yellow fever in Salvador, Brazil to determine the risk for human disease. The researchers studied the temporal and spatial distribution of the yellow fever virus outbreak affecting non-human primates (small monkeys) in Salvador, by geocoding the places where the monkeys were found dead. They also collected mosquitoes at such places to investigate potential vectors. The authors found that cases of yellow fever in  in densely urbanized areas posed a considerable risk for disease resurgence in humans because of the high prevalence of the A aegypti and A albopictus mosquitoes. Salvador has long been an epicenter of dengue transmission and more recently of Zika and chikungunya viruses, all with A aegypti as the main vector.
The authors conclude that surveillance and increased vaccination, even among those not considered at high risk for infection, could help to prevent human cases of  in Brazil.

Wednesday, November 1, 2017

Yellow fever virus found in semen of Brazilian patient

SHOW CITATION
October 27, 2017
Researchers in Brazil recently detected yellow fever virus RNA in urine and semen samples from a convalescent patient in Brazil.
Yellow fever is normally detected in blood, but urine has been used to confirm yellow fever infection in humans, researchers from two universities and a research institute in São Paulo noted in their reportBut yellow fever was not among the 27 viruses previously identified to persist in semen.
The researchers said their findings “suggest that semen can be a useful clinical material for diagnosis of yellow fever and indicate the need for testing urine and semen samples from patients with advanced disease.”
“Such testing could improve diagnostics, reduce false-negative results and strengthen the reliability of epidemiologic data during ongoing and future outbreaks,” they wrote in Emerging Infectious Diseases.
A recent yellow fever outbreak in Brazil was fueled by cases among monkeys in the Amazon basin and other tropical forests in Brazil, rather than person-to-person transmission involving mosquitoes. Following a large vaccination campaign, Brazil declared an end to the outbreak in September.
According to the researchers, there were 792 confirmed cases and 274 deaths in the Brazilian outbreak as of July 10. Their report summarized the case of a man aged 65 years from São Paulo who was not vaccinated against yellow fever.
According to the researchers, the man had traveled to the southeastern Brazilian state of Minas Gerais on Dec. 28, not long after the first cases of yellow fever were detected there. About a week later, he traveled to a rural area north of São Paulo. Three days after that, on Jan. 6, he began experiencing symptoms of infection, including fever, chills, body pain and nausea, according to the researchers.
More severe symptoms developed, and the man was admitted to several different hospitals over the next few weeks, according to the report. On Jan. 16, he was admitted to a reference hospital for infectious diseases in São Paulo. Serum samples taken there were negative for yellow fever, but a urine sample obtained 10 days after symptom onset was positive for the virus, the researchers reported.
Urine and semen samples taken on Jan. 27 also were positive for yellow fever virus by qRT-PCR. The researchers tested the urine sample to evaluate infectivity and isolated the virus in cell culture, confirming virus integrity. They confirmed infectivity after a second virus passage. The researchers did not mention testing the semen sample for viable virus. – by Gerard Gallagher
DisclosuresThe authors report no relevant financial disclosures.

PERSPECTIVE

Photo of Thomas Yuill
PERSPECTIVE
The detection of yellow fever virus in urine and semen when it is undetectable in blood suggests an additional approach to making a yellow fever diagnosis. Viable virus in urine and evidence of virus in semen raises a question about the risk for sexual transmission. It also raises the question about possible effects that yellow fever virus infection might have on male fertility as it does with infection by the related Zika virus. These results are from a single case. Considerably more cases need to be studied to determine how frequently yellow fever virus is shed in urine and semen and for low long before any firm conclusions can be drawn.
Thomas M. Yuill, PhD
ProMED virus diseases moderator
Professor emeritus, department of pathobiological sciences and department of forest and wildlife ecology
University of Wisconsin-Madison
Disclosure: Yuill reports no relevant financial disclosures.

Saturday, October 21, 2017

WHO supports the immunization of 874 000 people against yellow fever in Nigeria, Oct 2017

 The Government of Nigeria has launched a campaign to immunize 873 837 people against yellow fever in the states of Kwara and Kogi.
The ten-day campaign began on Friday, 13 October 2017, and mobilizes more than 200 health workers and volunteers. It targets residents aged 9 months to 45 years old.
“This campaign aims to ensure that people living in high-risk areas are protected from yellow fever, and to prevent the disease from spreading to other parts of the country,” said Dr. Wondimagegnehu Alemu, WHO Nigeria Representative.
WHO has been working with health authorities on its implementation in nine local government areas in Kwara State and two in Kogi State.
Nigeria has requested support from the International Coordination Group (ICG) on vaccine provision for yellow fever. A global stockpile of 6 million doses of the yellow fever vaccine is available for countries to access, with the support of Gavi, the Vaccine Alliance.
WHO and health partners have been supporting the Government’s response to the outbreak since the first case of yellow fever was confirmed in Oke Owa Community, Ifelodun Local Government Area of Kwara state on 12 September.
WHO has deployed experts to Nigeria to support surveillance and investigation, lab testing, public health measures, and engagement with at-risk communities. An Emergency Operations Centre has been activated in the area to coordinate the response.
The last yellow fever outbreak in Nigeria was reported in 2002, with 20 cases and 11 deaths.

For further information, please contact:

Fadéla Chaib
Communications Officer
Telephone: +41 22 791 3228
Mobile: +41 79 475 5556
E-mail: chaibf@who.int

Friday, October 6, 2017

Dengue and yellow fever: two Kenyan cities at high risk, Oct 2017

study published in PLOS One last month (17 August) shows that poor urban planning in Kenya could aid the re-emergence of dengue and yellow fever, transmitted through mosquitoes: Aedes aegypti and Aedes bromeliae.

Dengue, a viral disease spread by day-biting mosquitoes, “is the fastest spreading vector-borne viral disease” and has reached more than 100 countries, according to the WHO. Patients with the non-severe form of dengue develop high fever, flu-like symptoms and stomach pain, the severe form could result in the death of 20 per cent of patients with the disease. Meanwhile, yellow fever, a viral disease spread by infected mosquitoes could kill about 50 per cent of those infected with its severe form within seven to ten  days, says WHO.

“Our study is helping to identify areas where the vector is present in high abundance that can sustain transmission of the virus.”

Rosemary Sang, Kenya Medical Research Institute


The study was conducted in the outskirts of three Kenyan cities — Nairobi and Kisumu, which have no known history of dengue outbreak and Mombasa, which is prone to dengue outbreak — from October 2014 to June 2016 during the wet and dry seasons.
Researchers from Kenya-based International Centre of Insect Physiology and Ecology (icipe) and South Africa’s University of Pretoria measured the abundance of the mosquitoes Ae. aegypti and Ae. bromeliae.

According to the study, 7,424 Ae. aegypti and 335 Ae. bromeliae were collected from all sites, made up of 100 houses for each city and season.

Ae. aegypti remains the only known dengue vector in Kenya with sufficient abundance in the major cities to sustain transmission,” the authors note. “It is highly abundant and the risk values are indicative of high risk of dengue transmission in Kilifi and Kisumu.”

Rosemary Sang, a co-author of the study and a consultant scientist at the icipe, tells SciDev.Net that dengue outbreak in Kenya has only occurred in few specific locations in the coast and that the research team “wanted to establish the risk of spread of outbreaks to other areas”.

Sang, a principal research scientist at the Arbovirology Unit, Kenya Medical Research Institute, adds that more experiments are underway to determine if these vectors can transmit the viruses.

“Our study is helping to identify areas where the vector is present in high abundance that can sustain transmission of the virus should the disease get imported through infected travellers from outbreak countries or regions,” explains Sang, adding that this will be important for early warning and implementation of preventive measures.

Omu Anzala, a professor of medical microbiology at the University of Nairobi, lauds the study for increasing knowledge and understanding of newly emerging pathogens. “Being able to understand and predict whether there is impending epidemic is very important,” Anzala tells SciDev.Net. “We should be doing this regularly, looking at indicators of early warning so that we are better prepared [during disease outbreak].”

Anzala encourages research uptake by policy makers to enable them act quickly on outcomes of studies on emerging disease outbreaks.   
 
This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.
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