Alarmed that an outbreak of yellow fever in southwest Africa could spread if not quickly contained, medical experts will convene this week to consider whether to declare an international health emergency.
Though the panel convened by the World Health Organization may not make the declaration -- a move taken with Ebola and Zika outbreaks -- the session to be held in Geneva on Thursday speaks to the seriousness of the disease's spread in Angola. Yellow fever infections tied to Angola already have been reported in China.
"In my view calling an emergency committee for yellow fever is clearly the right thing to do," Lawrence Gostin, faculty director of Georgetown University's O'Neill Institute for National and Global Health Law, said in an email.
"First, there is the potential for rapid spread to other countries and regions, threatening the health of large populations in Africa, Asia and elsewhere," Gostin said. "Second, as the crisis escalates, global supplies of the yellow fever vaccine are dwindling and we could easily face a critical shortage. What this new emergency committee demonstrates is that mosquito-borne diseases — Zika and now yellow fever — pose major threats. This requires a war against mosquito vectors with resources and a full range of technologies, as well as health education."
In a paper published this month in the Journal of the American Medical Assn., Gostin and his colleague Daniel Lucey, an immunologist at the O'Neill Institute, called for WHO to “urgently convene an emergency committee to mobilize funds, coordinate an international response, and spearhead a surge in vaccine production.”
The disease emerged last December in Angola, which had not had an outbreak in almost 30 years. Since then, 2,267 suspected infections have been reported and 293 people have died from the virus, according to WHO.
Meanwhile, the disease has been imported by travelers from Angola to Kenya, China and the Democratic Republic of Congo, raising the alarm in other nations, including Namibia and Zambia that share a long border with Angola. An unrelated bout of yellow fever has also taken hold in Uganda.
“The risks for other countries really depend on how fast the cases are detected and the density of mosquitoes,” Sylvie Briand, WHO's director of the pandemic and epidemic diseases department, told reporters at a briefing in Geneva last week. “We are concerned for other countries that may have high density of mosquitoes.”
Yellow fever is transmitted by Aedes aegypti mosquitoes, which also carry Zika, the virus linked to severe birth defects that have swept South America in recent months.
Patients with severe infection from yellow fever experience high temperatures, jaundice, bleeding and eventually shock and failure of multiple organs. Between 20% to 50% of those who become jaundiced, entering what is known as the “yellow” phase of the disease, die from the virus, WHO officials said.
The outbreak in Angola is particularly worrisome because it is happening in urban areas, such as the capital city Luanda, where the first cases in the country were detected, health officials said.
"You have trillions of mosquitoes and millions of people, so the capacity of transmission of the virus is multiplied enormously,” said Briand. The virus is far easier to fight in sparsely populated rural areas, she said.
While there is no treatment for yellow fever, the vaccination used to prevent the disease is highly effective. But the global supply of the vaccine is limited, according to information published WHO. The agency said that because of the current outbreak, shipments of the vaccine that would ordinarily be used in routine immunization programs in other countries where yellow fever is endemic were being used in Angola and other affected countries.
Even before the yellow fever outbreak, the emergence of other infectious diseases, such as Zika, has prompted some health specialists to call for overhauling how to respond to potential global health threats.
Gostin and Lucey are among health specialists and academics who are calling for the creation of a permanent committee that would devise a “quick and effective” plan of action and respond as soon as new threats emerge.
Prior delays in convening such committees for the Ebola virus, and possibly the ongoing Zika epidemic, “cost lives and should not be repeated,” the academics wrote in their recent paper.
An explosion of yellow fever is not farfetched given the challenges of controlling the spread of the virus. While more than 105 million Africans have been vaccinated since 2006 when WHO launched a yellow fever initiative, several African nations still are not completely protected against the disease.
Combating yellow fever is made more challenging because victims don't show definitive symptoms until the disease has progressed, making early detection difficult.
Such was the case in Angola where an infected person was initially thought to have died of food poisoning after eating at an open-air marketplace restaurant. Two or three days later, a few more people, friends of the first victim, also died. They had all eaten at the same restaurants, so food poisoning was again suspected. Subsequent tests done at a lab outside Angola revealed yellow fever, Briand said. The owner of the restaurant, which reportedly had many mosquitoes, also died.
Llanos Ortiz, deputy desk manager for the emergency unit of the medical humanitarian organization Doctors Without Borders, said she was particularly concerned about the infection spreading in places such as Kinshasa, capital of the Democratic Republic of Congo, with its teeming population, high number of mosquitoes and access to travel to other regions and countries.
“Those urban settings are very well connected with the rest of the world,” said Briand of WHO. “Unfortunately, many people don’t take seriously enough the issue of vaccinations for travelers. This is why we have had many cases exported.”
“The looming fear is a yellow fever outbreak in Asia,” where the disease is not currently endemic, said Lucey, the Georgetown immunologist.
China has reported 11 yellow fever cases of individuals infected in Angola, according to WHO.
Ray Arthur, director of the Global Disease Detection Operations Center at the Centers for Disease Control and Prevention, said in emailed comments that there had been no local transmission of yellow fever in the U.S. since the early 1900s. And while many areas in the country have mosquitoes that can become infected and transmit yellow fever virus, the agency was “not expecting local transmission of yellow fever in the continental United States, ” Arthur said.
However, the CDC is “concerned about travelers going to Africa and South America,” where yellow fever is endemic, Arthur said. “Travelers can return to the United States with a yellow fever virus infection.”
The agency is advising travelers to countries with yellow fever to review the vaccine recommendations and requirements to determine their need for vaccinations.