According to Angolan Health Minister, Luis Sambo, the disease has now spread to 16 of the country's 18 provinces, despite a preventative vaccination campaign launched in February which reached 6 million of the capital's 7.4 million inhabitants.
"We need to increase the response capacity ... in both technological resources (such) as medicines and vaccines, as well as in personnel," said Sambo.
There is no cure for yellow fever, but there is a vaccine which protects people from contracting the disease.
However supplies of the vaccine are low, according to the WHO (which sent 6 million doses of the vaccine to Angola) the global emergency stockpile of vaccines is already empty.
Once contracted, the yellow fever virus incubates in the body for 3 to 6 days, followed by infection that can occur in one or two phases. The first, "acute", phase usually causes fever, muscle pain with prominent backache, headache, shivers, loss of appetite, and nausea or vomiting. Most patients improve and their symptoms disappear after 3 to 4 days.
However, 15% of patients enter a second, more toxic phase within 24 hours of the initial remission. High fever returns and several body systems are affected. The patient rapidly develops jaundice and complains of abdominal pain with vomiting. Half of the patients who enter the toxic phase die within 10 to 14 days, the rest recover without significant organ damage.
At risk are 44 endemic countries in Africa and Latin America, with a combined population of over 900 million. In Africa, an estimated 508 million people live in 31 countries at risk. The remaining population at risk are in 13 countries in Latin America, with Bolivia, Brazil, Colombia, Ecuador and Peru at greatest risk.
Small numbers of imported cases occur in countries free of yellow fever.
Several different species of the Aedes and Haemogogus mosquitoes transmit the virus, which is an arbovirus of the flavivirus genus, and the mosquito is the primary vector. It carries the virus from one host to another, primarily between monkeys, from monkeys to humans, and from humans to humans.
There is no specific treatment for yellow fever, only supportive care to treat dehydration, respiratory failure, and fever. Associated bacterial infections can be treated with antibiotics. Supportive care may improve outcomes for seriously ill patients, but it is rarely available in poorer areas.
Vaccination is the single most important measure for preventing yellow fever. In high-risk areas where vaccination coverage is low, prompt recognition and control of outbreaks through immunisation is critical to prevent epidemics. To prevent outbreaks throughout affected regions, vaccination coverage must reach at least 60% to 80% of a population at risk.
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 yellow fever vaccine is not needed.
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