- Three people dressed in baby suits and blue plastic glasses form a human conveyor belt to chicken embryos . The first has a tray of eggs that were injected with a vaccine against virus yellow fever, and then incubated for 4 days, and cut the top of each egg. The second tweezes embryos on the eggs and places them in a large bottle. The last person added a little liquid and then merges the embryos in a rich red broth that contains millions of weakened virus particles.
The end result of this process, repeated dozens of times each week at the Pasteur Institute in Dakar, is a very effective vaccine that provides lifelong protection against yellow fever . But the 80-year-old process is decidedly low-tech and hard to scale up and that became a problem because a large yellow fever epidemic that began in December 2015 Luanda, capital of Angola, emptied the strategic reserves of the world of vaccine.
Institut Pasteur, which makes about 10 million doses a year, is one of four facilities in the world producing shots for yellow fever, joining two plants operated by the government in Russia and Brazil and french vaccine company Sanofi Pasteur. Their combined production has long been at the height of the world's needs, and the epidemic in Angola has worsened the deficit. Another example of hatching for most in Asia, where yellow fever has never set foot-may be impossible to control, said Jack Woodall, a virologist retired in London, formerly the Centers for Disease Control and Prevention and the World health Organization. "I hate to be an alarmist," said Woodall, who is also a moderator at the Emerging Disease Surveillance System, an online warning system for epidemics. "But this is something I'm really panic about."
vaccine is the only bulwark against yellow fever, a dreaded killer without a remedy that is mainly transmitted through the bite of Aedes aegypti , also known as mosquito yellow fever. Most infected people have no symptoms at all; some experience fever, joint pain and headaches. But progress roughly 15% to a more severe stage in which the eyes and skin turn yellow; they may also bleed from the eyes, nose and mouth. Up to half of these severe cases are fatal. Although yellow fever is endemic in much of Latin America, Africa Door far the heaviest burden. Exact figures are difficult to find, but a study published in 2014 in PLOS Medicine estimated that the disease kills 78,000 Africans each year, although many experts felt that this number was too high.
Most infections occur in or near the jungle where mosquitoes spread the virus primarily between monkeys and sometimes infect a human viewer. urban households, such as Angola, can be much more serious, because mosquitoes can transmit the virus from person to person. "This is when the disease can really take off," said William Perea, the control of the World Health Organization (WHO) department of epidemic in Geneva, Switzerland. Angola has seen 40 confirmed cases and 198 deaths to date, but experts say the real toll could be 10 times higher. "We have not seen an epidemic like this for many years," said Perea.
A massive immunization campaign launched in February has already reached almost 6 million of about 7.5 million people in Luanda. But the disease has since spread to six of the 18 provinces of the country and the overall emergency stock of 6 million vaccines is empty. "This is certainly a stressful situation," said Melissa Malhame of Gavi Alliance for Vaccines, a public-private partnership based in Geneva, which aims to increase immunization in poor countries.
A ramp -up in battle against yellow fever had already stretched global supply of vaccine. many countries have done the shooting part of their routine immunization programs for children, while the catch-up campaigns massive were launched to protect entire populations who never received the vaccine before. a report of the United Nations emergency Fund last year found that the organization needed 42% more vaccines over the next 3 years than is available. A 2013 report put global output in 09 to 75 million doses, against 30 million in 00, but well below the 105 million doses needed this year. Production annual exact day is unknown, but it is probably about 80 million doses, said Tom Monath, a virologist who studied yellow fever for decades and is currently working on NewLink Genetics, a biotechnology company in Ames, Iowa. To make matters worse, the factory in Dakar is about to close for renovation 5 months.
Things can get better in the long run. Demand for the vaccine is expected to decline in a few years after the countries wrap their catch-up campaigns. The Pasteur Institute is building a new facility in Diamniadio, about 30 kilometers from Dakar, which could triple production by 2019; Sanofi Pasteur has built a new factory in France.
Meanwhile the WHO has urged Angola to vaccinate only in areas where yellow fever is spreading. But infected travelers have already made Angola the disease to three other African countries including the Democratic Republic of Congo; if the disease began circulating in its sprawling capital Kinshasa which could be catastrophic, said Monath.
"I think all the specialists in my field agree that there is a real and present danger of having a major yellow fever epidemic that is out of control," adds medical entomologist Paul Reiter of the Pasteur Institute in Paris. " It is a time bomb, "an interim measure could be to reduce the dose of vaccine, Monath said. Some studies have shown that only one-fifth or one-tenth of the current dose may protect people.
spread to Asia is the nightmare scenario for experts from yellow fever. Angola is the many Chinese workers home, and in at least six cases, they have already brought the virus in China. Five of these cases were in Beijing where Aedes aegypti does not occur, so that the disease could not spread. But the mosquito is abundant in southern China and elsewhere in Asia and are therefore vulnerable. Surprisingly, however, yellow fever never took off in Africa.
There a real and present danger of having a major epidemic of yellow fever that is uncontrollable.
Maybe that Asia has just been incredibly lucky. "It has not happened before, but does that mean he's not going to happen now?" Perea request. "Nobody knows."
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