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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.
Source

Over 6000 receive free yellow fever vaccination in Uganda, Oct 2017

By Ritah Kemigisa:
Over 6000 people have been immunized in the three day free yellow fever campaign  organized by the National Medical Stores and the ministry of health that ends today to reward tax payers.
Speaking to Kfm at Kololo independence grounds on the last day of the URA tax payers appreciation week, the NMS General Manager Moses Kamabare says by the end of today more than 10,000 people are expected to be immunized and issued with yellow fever cards.
Kamabare says due to the overwhelming turn up of people the ministry of health together with NMS have decided to add more five days for the free services adding that come next week the services shall still be offered to the people at Kololo independence grounds.
Kamabare adds that as a government policy only people with national identification cards are allowed to access the free services.
According to the Ministry of Health and Civil Aviation Authority, all passengers traveling in and out of Entebbe International Airport are supposed to present proof of immunization against the disease inform of certificates or cards.

Experts Alarmed by Yellow Fever Cases in Asia, Oct 2017

Eleven cases of yellow fever (YF) brought to China in 2016 were quickly contained but set off fear that the disease might gain a foothold in Asia, where 1.8 billion unvaccinated people could be at risk.
The introduction, by workers returning to China from Angola, highlight the dire straits epidemiologists face in trying to contain a disease with limited vaccine supplies. Shortages of YF vaccine developed because of outbreaks and the need for mass vaccinations in Angola and Brazil. By July 24, 2017, stocks of the only YF vaccine approved in the United States had been depleted, and supplies are not expected to become available for routine civilian use again until mid-2018.
Daniel R. Lucey, MD, MPH, and Halsie Donaldson, MS, both from the Division of Infectious Diseases, Georgetown University Medical, Washington, DC, write that the new risk for YF in Asia means that "the global vaccine stockpile must contain more than the projected 1.38 billion doses needed to eliminate existing YF epidemics by 2026." They published their findings online September 25 in Annals of Internal Medicine. The authors also explain that the 80-year-old, egg-based method currently used to manufacture YF vaccine cannot be scaled up quickly enough to stop urban epidemics.
"Thus, new YF vaccines based on cell culture and DNA technologies should be developed now, rather than in the mid to long term cited in the [World Health Organization's] Global Strategy to Eliminate Yellow fever Epidemics," the authors write.
Peter Hotez, MD, PhD, dean of the National School of Tropical Medicine, professor of Pediatrics and Molecular & Virology and Microbiology, and head of Pediatric Tropical Medicine at Baylor College of Medicine, Houston, Texas, agreed that new methods for producing YF vaccine are urgently needed, even without the potential for YF outbreaks in Asia.
"With regard to Asia, it remains somewhat of a mystery as to why YF has not spread there, as has Japanese encephalitis. Some have speculated that circulating dengue and [Japanese encephalitis] strains may provide some cross-protective herd immunity, but we really don't know the answer," Dr Hotez told Medscape Medical News. "But there are 3 million Chinese working in Africa now, through their belts-and-road initiative, and there is a theoretical threat to Asia. Moreover, we can be sufficiently concerned about YF in the western hemisphere and Africa alone to raise the issue of YF vaccine shortage."
Dr Hotez said that Dr Lucy and Donaldson are right to be concerned about the potential for YF outbreaks in both Africa and the Americas, as well as the possibility of YF vaccine shortages. "In the western hemisphere, we have seen during the last few years the rise of dengue, Zika, chikungunya, and other arboviruses transmitted by Aedes aegypti, so the threat of YF is very real. This is due to shifts in poverty and climate change. The risk to other areas, including the United States, has been further heightened by increased population density in urban areas, making transmission more likely, and by the widespread presence of mosquitoes able to transmit the virus," he said.
However, Dr Hotez also echoed the comment by Seth Berkley, MD, chief executive from Global Alliance for Vaccines and Immunization, that emergency vaccine stockpiles should be the last line of defense against YF, after better mosquito control, routine YF immunization, and preemptive vaccination campaigns. According to Dr Berkley, emergency YF vaccine stockpiles are essential, but "if we have to call upon them, we have in some way already failed. They should be our last line of defense."
Dr Berkley notes that the current global emergency stockpile of YF vaccine is about 6 million doses, a supply that could be quickly exhausted if Rio (population 12 million) and one other major city had YF outbreaks.
Meanwhile, shortages in the United States are already limiting the availability of YF travel vaccinations, which are required for travelers to enter some countries.
Dr Hotez told Medscape Medical News that part of the problem is the demand for YF vaccine has not been high until recently. "There is not always a high market incentive for vaccine manufacturers to make vaccines for pandemic threats, which is why the new organization [Coalition for Epidemic Preparedness Innovations] has been established," he said.
In the United States, YF vaccination is not routinely recommended except for patients traveling to an endemic area. Containing a potential outbreak is likely to be complicated by the fact that few US physicians have ever seen a case of YF, which causes a self-limited fever in 85% of patients but black vomit; bleeding from nose, mouth, and eyes; jaundice; and renal damage in the other 15%, half of whom die from the infection.
The authors and Dr Hotez have disclosed no relevant financial relationships.
Ann Intern Med. Published online September 26, 2017. Abstract
Source (nneds free registration)

Friday, September 29, 2017

Yellow Fever Vaccine Shortages in the United States and Abroad: A Critical Issue, Annals of Internal Medicine, Sept 2017

Yellow fever (YF) virus, a flavivirus that infects the liver, causes a self-limited febrile syndrome in 85% of patients. In the other 15%, however, it causes jaundice, bleeding, and renal damage, and half of these patients die. No antiviral therapy exists. In urban settings, YF virus is transmitted between humans by Aedes aegypti mosquitoes, as are Zika, dengue, and other viruses. Outside urban settings, in the jungle or forest (“sylvatic cycle”), YF transmission occurs between monkeys and from monkeys to humans via non-Aedes mosquitoes (1).

The United States had YF epidemics in the 18th and 19th centuries. In the 20th century, epidemics occurred in sub-Saharan Africa, Latin America, and the Caribbean. The first cases in Asia were reported in 2016, when 11 workers returned home to China after having been infected in Angola (1).

How Nigeria is tackling spread of yellow fever? Sept 2017

The Federal Government on Tuesday expressed its readiness to contain further spread of yellow fever in the country.
The Chief Executive Officer, Nigeria Centre for Disease Control, NCDC, Chikwe Ihekweazu, said this in a statement he issued in Abuja.
He also said that the government would also limit the impact of the killer ailment.
Mr. Ihekweazu said that following the case of yellow fever in Kwara State, laboratory diagnosis was carried out at the Lagos University Teaching Hospital and confirmed at the Institute Pasteur, Dakar, Senegal.
He said that a multi-agency Incident Management System has been constituted at the NCDC to ensure a rapid and coordinated response.
”In response to the case, and in line with WHO guidelines, a vaccination campaign is being planned to begin in the affected and surrounding Local Government Areas on 30th September to prevent further spread.
”Communication activities are being intensified to enlighten health care workers and the general public,’’ he said.
He also said that an Emergency Operations Centre is being activated in the state to ensure a coordinated and efficient response at the state level.
The NCDC boss described yellow fever as an acute viral haemorrhagic disease transmitted by infected Aedes mosquitoes.
He listed the symptoms to include fever, headache, jaundice (yellowness of the eyes), muscle pain, nausea, vomiting and fatigue.
According to him, some infected people may not experience any of these symptoms, while in some the symptoms might be mild.
He added that in severe cases, jaundice and bleeding may occur from the mouth, nose, eyes or stomach.
Ihekweazu said that vaccination against the disease remained the most important measure in preventing Yellow Fever.
He said the Yellow Fever vaccine had been part of the childhood immunisation schedule in Nigeria.
”Other methods of prevention include using insect repellents, sleeping under a long-lasting insecticide treated nets, living in net screened accommodation, ensuring proper sanitation and getting rid of stagnant water or breeding places for mosquitoes.
”Although there is no specific medicine to treat the disease, intensive supportive care can be provided, most patients would recover with appropriate care when they present early enough,” he said.
He, therefore, advised health care workers to practice standard precautions while handling patients or body fluids at all times and to be familiar with the case definition and maintain a high index of suspicion.
Mr. Ihekweazu advised Nigerians to remain calm, avoid self-medication and report to the nearest health facility if feeling unwell or if they notice any of the above symptoms in anyone around.

Tuesday, September 26, 2017

Mosquitoes carrying deadly diseases could invade 75% of America, warns US government, Sept 2017

Mosquitoes capable of spreading serious and potentially deadly diseases such as Zika, dengue and yellow fever could invade about three-quarters of mainland United States, the US Centres for Disease Control and Prevention have warned.
The CDC, a US federal agency, has previously warned that climate change could affect human health in many ways including increasing the number of “disease carriers such as mosquitoes and ticks”.
In a paper published in the Journal of Medical Entomology, it revealed maps showing areas where the habitat was suitable for two particular species of mosquito, Aedes aegypti or Aedes albopictus to survive.
mosquitomap.jpg
Mosquitoes could start spreading deadly diseases across a huge swathe of the US (CDC)
A study found 71 per cent of counties in the 48 contiguous states were suitable for aegypti and 75 per cent could support albopictus.
The paper said the dengue, chikungunya and Zika viruses in particular represented a “growing public health threat in parts of the United States where they are established”.
“We anticipate that Aedes aegypti and albopictus will be found more commonly in counties classified as suitable,” it said.
“Counties predicted suitable with 90 per cent sensitivity should therefore be a top priority for expanded mosquito surveillance efforts while still keeping in mind that Aedes aegypti and albopictus may be introduced, via accidental transport of eggs or immatures, and potentially proliferate during the warmest part of the year.”
Dr Rebecca Eisen, a research biologist with the CDC, said the maps showed the CDC’s “best estimate” of the insects potential range.
“In other words, these maps show areas where CDC predicts Aedes aegypti and albopictus mosquitoes could survive and reproduce if introduced to an area during the months when mosquitoes are locally active,” she said.
However the experts stressed the maps did not show where mosquitos were currently or the place where there was a risk of virus transmission. 
Temperature was a key factor.
If there was just one day in winter when the temperature exceeded 10 degrees Celsius (50F), the chances that the area would be suitable for mosquitoes increased.
Consistently cold temperatures, however, reduced the chances that the insects’ eggs would survive the winter, particularly for aegypti, Dr Eisen said.
Rainfall had a significant influence on albopictus as it relies more on water courses filled by rainwater to lay its eggs than aegypti.
Dr Eisen said the maps would help monitor for signs the mosquitoes.
“Surveillance efforts can be focused in counties where Aedes aegypti and albopictus could survive and reproduce if introduced to an area during the months when mosquitoes are locally active or at least survive during summer months if introduced,” Dr Eisen said. 
“Additionally, the maps can help healthcare providers and the public understand where these types of mosquitoes could be found so that they can take steps to protect against mosquito bites and possible infection."

Nigerian govt confirms new yellow fever case, Sept 2017

A case of Yellow Fever has been confirmed in Oke Owa in Ifelodun Local Government Area of Kwara State, says the Federal Ministry of Health.
In a press statement released on Monday, the ministry said the case was confirmed in a young girl from the community after a laboratory diagnosis at the Lagos University Teaching Hospital at the Institut Pasteur, Dakar, Senegal on the September 12.
Following the confirmation of the case, the Minister of Health, Isaac Adewole, said the State Epidemiology Team has begun investigation into the affected area and neighbouring communities.
“A joint team from the Nigeria Centre for Disease Control, National Primary Health Care Development Agency and the World Health Organisation Country Office has been deployed to support the State in carrying out a detailed investigation and risk analysis,” he said
Mr. Adewole added that an Outbreak Control Team had also been constituted to ensure rapid and coordinated decision-making.
He assured the public that all the agencies of the Federal Ministry of Health and their partners would work together to support the government of Kwara to respond in order to prevent spread.
Yellow fever is an acute viral haemorrhagic disease transmitted by infected aedes mosquitoes.
The disease is preventable, the most important measure to in prevention being vaccination against the disease.
A single dose of Yellow Fever vaccine is part of Nigeria’s routine immunisation schedule given to children at nine months and the dose is sufficient to confer sustained protection of up to 10 years.
It is meant to be given free at all primary healthcare centres and other children immunisation point .
According to fact sheets on the disease from the World Health Organization, yellow fever virus is endemic in tropical areas of Africa and Central and South America.
The international health agency said a small proportion of patients who contract the virus develop severe symptoms and approximately half of them die within seven to 10 days.
But since the launch of the Yellow Fever Initiative in 2006, significant progress has been made in combatting the disease in West Africa and more than 105 million people have been vaccinated in mass campaigns.
There is currently no specific anti-viral drug for yellow fever.
Mr. Adewole said a vaccination campaign is already being planned in the affected area in Kwara State to prevent spread.
Symptoms of the disease include fever, headache, jaundice, muscle pain, nausea, vomiting and fatigue.
Some infected people may, however, not experience any of these symptoms. In severe cases, bleeding may occur from the mouth, nose, eyes or stomach.
Other methods of prevention include using insect repellent, sleeping under a long-lasting insecticide treated net, ensuring proper sanitation and getting rid of stagnant water or breeding space for mosquitoes.
Mr. Adewole advised health care workers to practise universal care precautions while handling patients at all times and also urged to be alert and maintain a high index of suspicion.

Wednesday, September 13, 2017

H7N9 Avian Flu Continues to Spread, Worsen in China, Medscape Sept 2017

The latest epidemic of Asian lineage avian influenza A (Asian H7N9) in China infected almost as many patients as the four previous outbreaks combined and gave rise to a variant less susceptible to available treatments and vaccines, researchers report in an article  published in the September 8 issue of the Morbidity and Mortality Weekly Report.
The fifth annual epidemic, which occurred from October 1, 2016, through July 31, 2017, included 759 patients and 281 deaths (37%). The cumulative mortality for all five Asian H7N9 outbreaks since February 2013 is 39% (605 of 1557 patients).
"Although human infections with Asian H7N9 viruses from poultry are rare and no efficient or sustained human-to-human transmission has been detected, when human infections do occur, they are associated with severe illness and high mortality," write James C. Kile, DVM, from the Influenza Division at the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and colleagues. "Continued vigilance is important to identify changes in the virus that might have epidemiologic implications, such as increased transmission from poultry to humans or transmission between humans."
The fifth outbreak involved all but three of 33 provinces, regions, and municipalities in China. All infected patients had either lived in or traveled to these areas, and most (90%) infections were associated with poultry exposure, especially at live bird markets.
The authors note, however, that the increase in infections was the result of wider geographic spread and higher prevalence of Asian H7N9 viruses among poultry, not increased poultry-to-human or human-to-human transmission.
Notably, during the fifth epidemic, some Asian H7N9 strains acquired mutations that turned them from low-pathogenic to high-pathogenic strains. Twenty-seven patients were infected with high-pathogenic avian influenza strains that had acquired mutations.
Sequencing data from 166 viral isolates collected during the fifth epidemic uncovered genetic markers of resistance to amantadine and rimantadine. In addition, researchers found significant changes in surface proteins among some of the high-pathogenic avian influenza strains, making them less similar to previous candidate vaccine viruses.
These factors contributed to the CDC's decision to classify Asian H7N9 as the virus with the highest potential pandemic risk among all viruses evaluated using the Influenza Risk Assessment Tool.
The government of China is trying to minimize Asian H7N9 spread by promoting large-scale farming and centralized slaughtering, improving poultry product handling, and routinely closing, cleaning, and disinfecting live poultry markets and enhancing surveillance for influenza-like illness.
The authors write, "CDC has partnered with China CDC, and other China government organizations, United Nations organizations, and surrounding countries to enhance surveillance and laboratory capacity to detect and respond to Asian H7N9 in animals and humans."
One coauthor holds two US patents for influenza vaccines. The other authors have disclosed no relevant financial relationships.
Morb Mortal Wkly Rep. 2017;66:928-932. Full text  

Saturday, September 9, 2017

Yellow Fever Vaccine Shortage Affects Arkansas Travelers, Sept 2017

FAYETTEVILLE, Ark. -- - Yellow fever is a viral disease transmitted by infected mosquitos. 
 
The depletion of the US-made vaccine means an alternative vaccine,manufactured in France, will have to be imported. 
 
"We are down to our last few right now so we will have to refer students and faculty who are in need of the vaccine to other clinics who do stock the current yellow fever vaccine that is there," Executive Director, Pat Walker Health Center Mary Alice Serafini.  
 
The disease impacts people in almost 50 countries, including South America and Africa. 
 
Health officials say if you're told to get the vaccine before visiting a certain country, do it. 
 
"Not only is the person at risk for yellow fever once they are there, but it is possible that they could be infected and bring it back," Medical Director for Immunizations, Arkansas Dept. of Health Dr. Jennifer Dillaha said. "Although we do not have yellow fever currently the united states, we have had serious yellow fever epidemics in history."
 
The shortage is so widespread, the only clinic with the vaccine in the state is in Little Rock. 
 
"Any travel clinic is equipped and trained on these types of things and make recommendations for the kind of health risks people will encounter and how they should overcome the health risks," Dr. Dillaha said. 
 
Travelers in Northwest Arkansas include study abroad students from the university. 
 
"We send a lot of students to Central and South America and Africa," Assistant Director, Office of Study Abroad at The University of Arkansas Brian Poepsel said. "Those students are going to have to work a little bit harder to obtain it. "

Friday, September 8, 2017

Brazil declares end to yellow fever outbreak that killed 261, Sept 2017

S
AO PAULO — Brazil’s Health Ministry has declared an end to a yellow fever outbreak that killed more 250 people over the past nine months.
The ministry said Wednesday that the last case of the mosquito-borne disease was in June. In total, 777 people were infected, of whom 261 died.
The outbreak was highly unusual in a country that typically sees a handful of cases each year. The disease also occurred in areas not previously considered at risk and where vaccination rates were low.
In response, Brazil mounted a massive vaccination campaign, sending out more than 36.7 million doses. Vaccination efforts are continuing since the ministry says the average coverage rate in areas that bore the brunt of the outbreak is around 60 percent, below the target of 95 percent.
https://www.statnews.com/2017/09/06/yellow-fever-outbreak-brazil-over/

Monday, September 4, 2017

Brazil's Yellow Fever Cases Wane, But Scientists Fear Resurgence, Sept 2017


There were no new cases of yellow fever reported in Brazil last month, a change from earlier this year when the country reported more than 700 cases, including those near big cities like Rio De Janeiro and Sao Paulo.
But scientists still fear a resurgence, especially as Brazil enters its summer months.
Here & Now's Meghna Chakrabarti speaks with writer Sam Kean(@sam_kean) who followed the trail of yellow fever and the push to prevent outbreak for Science magazine.


This segment aired on August 29, 2017.

Yellow fever – France – French Guiana - WHO Update, Sept 2017

On 22 August 2017, the National IHR Focal Point for France notified a confirmed fatal case of yellow fever in a 43-year-old Brazilian woman in French Guiana, with an unknown vaccination status.
The patient was hospitalized on 7 August 2017 and died on 9 August 2017 at the Cayenne hospital from fulminant hepatitis. She may have visited a gold mining area near St. Elie (North center of the country). Investigations are currently ongoing in order to identify the patient's travel route.
On 21 August 2017, the case was laboratory confirmed at the national reference center for arboviruses, Institut Pasteur Cayenne by RT-PCR. This is the first confirmed case diagnosed in this territory since 1998.
In French Guiana, yellow fever is considered endemic. The overall immunization coverage is good as yellow fever vaccination is mandatory but immunization coverage might be low in specific populations like clandestine and illegal workers. Therefore, vaccination catch-up will be implemented in legal and illegal gold prospecting areas.

Public health response

French Guiana health authorities are implementing several public health measures:
  • An initial investigation was performed and further investigations are ongoing.
  • Vector control interventions are being implemented, especially in specific zones that the case visited. These include health facilities in Cayenne and Kourou, localities of the interior around Saint Elie, and in the Bas-Oyapock river area.
  • The feasibility of vaccination catch-up targeting workers in legal and illegal gold mining areas is considered.
  • Communication and messages on prevention measures for yellow fever are being disseminated in French Guiana, including to people who live in those areas.

WHO risk assessment

Yellow fever is an acute viral hemorrhagic disease that has the potential to spread rapidly and cause serious public health impacts in unimmunized populations. Vaccination is the most important means of preventing the infection.
French Guiana is considered at risk for yellow fever transmission. A yellow fever vaccination certificate is required for travelers over one year of age. Vaccination coverage in French Guiana is optimal, however, the coverage in some populations such as clandestine workers, in mining areas could be sub-optimal and therefore at risk for yellow fever infections.
While the exact place of infection remains under investigation, the most likely geographic area of infection appears to be around the border between French Guiana and Brazil along the Oyapock river.
At this stage and according to the preliminary data, this case is not epidemiologically linked to the sylvatic yellow fever outbreaks reported from Brazil since January 2017. Sequencing and comparison with yellow fever virus strains from other countries is needed to understand the potential link between the different outbreaks and the evolution of yellow fever virus. Based on the information currently available regarding epidemiological situation and early public health actions, the potential for large epidemic and international spread exists but is limited and could be further reduced by vaccination.

WHO advice

Advice to travelers planning to visit areas at risk for yellow fever transmission in South America includes:
  • Vaccination against yellow fever at least 10 days prior to the travel. A single dose of yellow fever vaccine is sufficient to confer sustained immunity and life-long protection against yellow fever disease. A booster dose of the vaccine is not needed.
  • Observation of measures to avoid mosquito bites.
  • Awareness of symptoms and signs of yellow fever in general population.
  • Promotion of health care seeking behavior while traveling and upon return from an area at risk for yellow fever transmission, especially to a country where the establishment of a local cycle of transmission is possible (i.e. where the competent vector is present).
This case report illustrates the importance of maintaining awareness of the need for yellow fever vaccination, especially in areas with favorable ecosystem for yellow fever transmission.
Yellow fever can easily be prevented through immunization provided that vaccination is administered at least 10 days before travel. A single dose of yellow fever vaccine is sufficient to confer sustained immunity and life-long protection against Yellow fever disease and a booster dose of the vaccine is not needed.
WHO, therefore, urges Members States to strengthen the control of immunization status of travelers to all potentially endemic areas. Viraemic returning travelers may pose a risk for the establishment of local cycles of yellow fever transmission in areas where the competent vector is present. If there are medical grounds for not getting vaccinated, this must be certified by the appropriate authorities.
WHO does not recommend that any general travel or trade restriction be applied on French Guiana based on the information available for this event.

Saturday, August 26, 2017

Gaps persist in global yellow fever vaccination coverage, Aug 2017

SHOW CITATION
August 24, 2017
Notable gaps in vaccination persist in areas at risk of yellow fever virus transmission, with approximately 393.7 million to 472.9 million people still in need of immunization to reach 80% population coverage recommended by WHO, according to recent findings.
“In many yellow fever risk areas, vaccine coverage remains too low to prevent outbreaks,” Freya M. Shearer, DPhil candidate from the Big Data Institute at Li Ka Shing Center for Health Information and Discovery, and colleagues wrote inThe Lancet Infectious Diseases. “The course of the Angolan outbreak and international response reiterates the need for a sustained policy of preventive vaccination of at-risk populations to reduce the risk of epidemics.”
Researchers examined global yellow fever vaccination coverage from 1970 through 2016 to calculate how many individuals still require vaccination to reach the population coverage thresholds for outbreak prevention recommended by WHO. They performed an adjusted retrospective analysis using data compiled from WHO reports and health-service-provider registries that included yellow fever vaccination information between May 1, 1939, to Oct. 29, 2016. Shearer and colleagues calculated three population coverage values representing alternative scenarios to account for any uncertainty in how vaccine campaigns were targeted. They then combined that information with demographic data and tracked vaccination coverage through time across countries at risk of yellow fever transmission.
Their analysis revealed significant increases in yellow fever vaccine coverage since 1970. However, prominent gaps still exist in coverage within risk zones in Africa and Latin America. An assessment of yellow fever vaccination coverage by age group in 2016 showed improvement of routine infant vaccination programs in protecting children at the country level, but also revealed gaps in adult populations for most countries. Many individuals (between 393.7 million and 472.9 million) require vaccination in areas at risk of yellow fever virus transmission to reach WHO’s recommended 80% population coverage threshold, the researchers said. This represents between 43% and 52% of the population within the areas at risk, compared with between 66% and 76% of the population who would have needed immunization in 1970.
“The results of this study highlight both important progress and gaps in yellow fever vaccination coverage within risk zones and provide credible estimates of the doses required for supplementary campaigns,” Shearer and colleagues wrote. “The risk of a yellow fever epidemic can be eliminated if effective vector control, vaccination and disease surveillance are enforced and maintained.”
Annelies Wilder-Smith
In a related commentary, Annelies Wilder-Smith, MD, PhD, MIH, professor of infectious diseases at Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, and president of the International Society of Travel Medicine, wrote that this study provides policymakers with the data crucially needed to control yellow fever.
“Absent or erratic control of proof of yellow fever vaccination at entry, falsified vaccine certificates, flawed risk assessments in travel medicine clinics, changing travel patterns and attitudes of travelers and inadequate information by travel medicine providers have led to preventable cases of yellow fever in travelers, which contributes to the spread into new areas,” she wrote. “Although the pre-emptive protection of endemic populations should be the main thrust, efforts should also be enhanced to contain outbreaks rapidly and to stop international spread. The onus is on the world to avoid vaccine shortfalls in the future.” – by Savannah Demko
Disclosures Shearer reports no relevant financial disclosures. Please see the study for all other authors’ relevant disclosures. Wilder-Smith reports no relevant financial disclosures.