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Yellow Fever: An OpenLearn reading list

Updated Tuesday, 16 August 2016
The World Health Organisation warns that an outbreak of Yellow Fever in DRC and Angola could, unchecked, become a global pandemic. Here's a guide to what you need to know about the disease.

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A public health announcement about dengue and yellow fevers in Paraguay A public health campaign about Yellow Fever and Dengue Fever in Paraguay

What is yellow fever?

The NHS explains the basics of the disease, including what to look for:

Yellow fever is a serious viral infection that is spread by certain types of mosquito. It’s mainly found in sub-Saharan Africa, South America and parts of the Caribbean.

The condition can be prevented with a vaccination and is a very rare cause of illness in travellers.

[...]

The symptoms of yellow fever occur in two stages. The initial symptoms develop three to six days after infection, and can include:

a high temperature (fever)
a headache
nausea or vomiting
muscle pain, including backache 
loss of appetite

This stage will usually pass after three to four days and most people will make a full recovery.

However, around 15% of people go on to develop more serious problems, including jaundice (yellowing of the skin and whites of the eyes), kidney failure and bleeding from the mouth, nose, eyes or stomach (causing blood in your vomit and stools).

Up to half of those who experience these symptoms will die.

Read at NHS Choices: Yellow Fever 

Why is Yellow Fever a global risk at the moment?

The Democratic Republic of Congo and Angola are seeing rising numbers of Yellow Fever cases; vaccines are designed to respond rapidly to small-scale crises rather than provide blanket protection for a population - and there's a risk of foreign workers falling ill and returning home. Emily Baumgartner visited the DNC:

There are reportedly 100,000 mostly unvaccinated Chinese construction workers and business people in Angola and an untold number in the DRC. An ill China-bound traveler from either country could trigger transmission among the 100 million people living in large Chinese cities. From there yellow fever could spread to any and all 100 countries that have endemic dengue globally.

“So, we should be very worried,” Woodall says. He also warns that health officials cannot necessarily rely on travelers’ paperwork to tell them who has been vaccinated. False yellow fever vaccination documentation has historically been less expensive to obtain than the vaccine itself. Given the gravity of the situation, he recommends that authorities vaccinate all travelers going to—or returning home from—countries with current outbreaks, including endemic countries in Latin America. “[At the least], screen international yellow fever vaccination certificates carefully for fakes. If facilities permit, vaccinate and quarantine arrivals with dubious documentation. Otherwise, send them home on the next flight,” Woodall says. “If you have to pay the return ticket, the airfare will cost less than … the economic disruption of [a global epidemic].”

And even though WHO has declined to deem this outbreak a “public health emergency of international concern,” or PHEIC, they, too, admit the threat of global spread is unnerving. “When you ask how afraid we are, the answer is that we’re trying to vaccinate over 30 million people this year in two large urban areas in Africa,” says Aylward, referring to the 20 million vaccines already used this year, along with the 15.5 million ahead. “That is completely unprecedented in recent history of yellow fever control measures. What we’re dealing with is a high consequence event here.”

Read at Scientific American: Could Yellow Fever Become the Next Pandemic?

It's not just Angola and DRC

Christina Faust of Princeton contributes to BioMed Central's Bug Bitten blog with an observation that other areas are suffering, too:

Currently, an additional seven countries (Brazil, Chad, Colombia, Ethiopia, Ghana, Peru and Uganda) are reporting yellow fever cases that are not related to Angola. While the Angolan outbreak has led to some exported cases, particularly to neighbouring DRC, these other countries have developing outbreaks that warrant surveillance. Another outbreak on the scale of Angola could lead to more deaths due to vaccine supplies running low.

At this time, the outbreaks are viewed as critical national public health issues, but arenot believed to be a Public Health Emergency of International Concern (PHEIC) . Priorities should be increasing vaccination, vector control, and case management in areas where transmission persists. Migrant workers and travellers in affected regions should also be vaccinated to prevent spread of the virus. Countries and areas with strong travel links to affected countries and with a local vector, such as China, should implement outbreak preparedness by improving surveillance and stockpiling emergency vaccinations.

Read at Bug Bitten: Yellow Fever cases on the rise in West Africa

How is the world responding?

If there's not enough vaccine to go round, scientists are hoping to make it stretch by using smaller amounts, with the hope it'll protect enough until the current challenge is over.  Kai Kupferschmidt explains:

WHO's emergency stockpile of yellow fever vaccine, which was depleted earlier this year, has been restocked and is now back to 5 million doses. But the Congolese government, worried that the virus could spread rapidly among Kinshasa's 10 million residents, has decided to stretch the 1.7 million doses it has received by giving people 0.1 milliliters of the vaccine each instead of the standard 0.5 milliliters.

The yellow fever virus is primarily transmitted by Aedes aegypti, the mosquito species that also spreads Zika and dengue. Most people who are infected have no symptoms, but about 15% develop serious disease, and about half these patients die. There is no cure, but the vaccine, although cumbersome to produce, is highly effective: A single dose confers lifelong protection.

Fearing that the disease could spread to Asia, which has never seen a yellow fever outbreak, some experts had urged governments and WHO to adopt the vaccine-saving strategy. In June, WHO's Strategic Advisory Group of Experts (SAGE) on Immunization concluded that the lower dose would still offer protection for at least 12 months. (The recommendation was made in an emergency session, but the group has planned a formal evaluation for October.) “We felt very comfortable with the data that was presented to go ahead and make the recommendation,” says SAGE chair Jon Abramson, a pediatrician at Wake Forest School of Medicine in Winston-Salem, North Carolina. “We feel the benefit of vaccinating as many people as we can far outweighs the small risk that somebody won’t respond who could have responded to a larger dose.”

SAGE advised that children under 2 years of age should receive the full dose, however, and it pointed out some practical problems as well, such as the need for millions of smaller syringes. A WHO spokesperson says that problem has been solved by using syringes stored in China and Denmark for polio vaccination programs.

Read at Science: Yellow fever emergency forces officials to combat virus with tiny dose of vaccine

How do we know about the causes and cures of Yellow Fever?

The history of investigations into Yellow Fever has been woven into a narrative by Yale's Wilbur G Downs:

Carter has written on the history of yellow fever. He studied in detail the passage of yellow fever through a community, attempting to define the incubation period of the disease. Josiah Clark Nott, a Connecticut native, settled in Alabama, had opportunity to study yellow fever at close hand in Alabama.

In one epidemic affecting Mobile, he lost four of his children, even though he had moved them to the country, outside of the stricken city. His observations on epidemic spread led him to postulate an insect vector for yellow fever.

His hypotheses are not precise, formulated as they were fifty years before the first demonstration of a mosquito vector of disease. Beauperthuy, a physician working in Angostura (later Ciudad Bolivar), Venezuela, advanced a similar hypothesis several years later. Nott was a keen observer and set forth clearly his views that yellow fever was what we would call today a disease with a wide spectrum of clinical manifestations, ranging from mild illness in many cases, sometimes with no or very low fever, to cases with a fulminating onset, often terminating, in but four or five days, in death.

Carlos Finlay, working in Havana, Cuba, advanced again the hypothesis of a mosquito vector of yellow fever, and backed up this hypothesis with experimental work, attempting to show that Aedes aegypti, then known as Stegomyia fasciata, could be infected by and transmit yellow fever.

The U.S. Army group in Havana, detailed to determine how yellow fever was spread, examined existing theories and was particularly impressed by Finlay's 1881 mosquito hypothesis. This, coupled with Carter's observations made in Mississippi in 1898, suggesting an incubation from first infecting case to later secondary cases of from two to three weeks, influenced Walter Reed and his associates to explore mosquito vectors. 

Read the full paper: History of Epidemiological Aspects of Yellow Fever

Does Yellow Fever occur as a plot in literature?

The 1799 novel, Arthur Mervyn Or Memoirs Of The Year 1793, by Charles Brockden Brown, has yellow fever running through its plotline - the protaganist runs into trouble trying to avoid being taken to hospital when he falls with the fever:

I wandered over this deserted mansion, in a considerable degree, at random. Effluvia of a pestilential nature assailed me from every corner. In the front room of the second story, I imagined that I discovered vestiges of that catastrophe which the past night had produced. The bed appeared as if some one had recently been dragged from it. The sheets were tinged with yellow, and with that substance which is said to be characteristic of this disease, the gangrenous or black vomit. The floor exhibited similar stains.

There are many who will regard my conduct as the last refinement of temerity, or of heroism. Nothing, indeed, more perplexes me than a review of my own conduct. Not, indeed, that death is an object always to be dreaded, or that my motive did not justify my actions; but of all dangers, those allied to pestilence, by being mysterious and unseen, are the most formidable. To disarm them of their terrors requires the longest familiarity. Nurses and physicians soonest become intrepid or indifferent; but the rest of mankind recoil from the scene with unconquerable loathing.

I was sustained, not by confidence of safety, and a belief of exemption from this malady, or by the influence of habit, which inures us to all that is detestable or perilous, but by a belief that this was as eligible an avenue to death as any other; and that life is a trivial sacrifice in the cause of duty.

I passed from one room to the other. A portmanteau, marked with the initials of Wallace's name, at length attracted my notice. From this circumstance I inferred that this apartment had been occupied by him. The room was neatly arranged, and appeared as if no one had lately used it. There were trunks and drawers. That which I have mentioned was the only one that bore marks of Wallace's ownership. This I lifted in my arms with a view to remove it to Medlicote's house.

At that moment, methought I heard a footstep slowly and lingeringly ascending the stair. I was disconcerted at this incident. The footstep had in it a ghost-like solemnity and tardiness. This phantom vanished in a moment, and yielded place to more humble conjectures. A human being approached, whose office and commission were inscrutable. That we were strangers to each other was easily imagined; but how would my appearance, in this remote chamber, and loaded with another's property, be interpreted? Did he enter the house after me, or was he the tenant of some chamber hitherto unvisited; whom my entrance had awakened from his trance and called from his couch?

In the confusion of my mind, I still held my burden uplifted. To have placed it on the floor, and encountered this visitant, without this equivocal token about me, was the obvious proceeding. Indeed, time only could decide whether these footsteps tended to this, or to some other, apartment.

My doubts were quickly dispelled. The door opened, and a figure glided in. The portmanteau dropped from my arms, and my heart's blood was chilled. If an apparition of the dead were possible, (and that possibility I could not deny,) this was such an apparition. A hue, yellowish and livid; bones, uncovered with flesh; eyes, ghastly, hollow, woe-begone, and fixed in an agony of wonder upon me; and locks, matted and negligent, constituted the image which I now beheld. My belief of somewhat preternatural in this appearance was confirmed by recollection of resemblances between these features and those of one who was dead. In this shape and visage, shadowy and death-like as they were, the lineaments of Wallace, of him who had misled my rustic simplicity on my first visit to this city, and whose death I had conceived to be incontestably ascertained, were forcibly recognised.

This recognition, which at first alarmed my superstition, speedily led to more rational inferences. Wallace had been dragged to the hospital. Nothing was less to be suspected than that he would return alive from that hideous receptacle, but this was by no means impossible. The figure that stood before me had just risen from the bed of sickness, and from the brink of the grave. The crisis of his malady had passed, and he was once more entitled to be ranked among the living.

Read at Project Gutenberg: Arthur Mervyn

 

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