Could Yellow Fever Return to the United States?

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In the summer-fall of 1878 an epidemic of yellow fever destroyed the city of Memphis, Tennessee.  Likely introduced into the Caribbean by trade from the West Coast of Africa and later brought up the Mississippi River by a steamer ship (the Emily B. Souder) with sick and dying sailors, yellow fever killed an estimated 5,000 Memphis residents, almost one-third of its population who did not flee the city that August [1].   According to Molly Caldwell Crosby in her detailed account, the summer-fall 1878 yellow fever epidemic in the Mississippi Valley was possibly “the worst urban disaster in American history” [1].

Among the factors responsible for the 1878 tragedy were an unusually warm winter and spring that year, which helped Aedes aegypti mosquitoes  to flourish in the Mississippi Valley, together with a lack of adequate urban drainage and a functioning sewer system, and a susceptible (non-immunized) population – the yellow fever vaccine would not be developed for another 50 years.

Today, the world’s yellow fever-endemic areas are restricted to Sub-Saharan Africa (figure image) and tropical regions of South America, but there are a few red flags suggesting the possibility that the “yellow jack” (a historical term used to once describe yellow fever) could return to the US.  The Ae. aegypti mosquitocan now be found in many areas of the southern United States.  This is an area where US poverty rates are at their highest, along with its fellow travelers poor urban housing and neglected foci of standing water.  The area has also experienced unusually warm winters and springs over the past few years.  Indeed, dengue fever, another arbovirus infection transmitted by Ae. aegyptimosquitoes, was recently shown to have emerged in Houston, Texas in 2003.  Although Max Theiler received the Nobel Prize for developing the yellow fever vaccine in 1951, vaccination rates in the US are practically non-existent except among travelers to endemic areas.

There are several examples of US vulnerability to yellow fever, including our home city of Houston, which has recently emerged as a true gateway city and globalization hub. For instance, today, Houston hosts the world’s largest number of Nigerians expats (who provide important and skilled expertise for our city’s oil and energy industry), and there are direct flights to and from Lagos, the largest Nigerian city.  A recent study from the Division of Global Migration and Quarantine of the CDC (Centers for Disease Control and Prevention) found thatUS travelers to Nigeria are especially likely to decline vaccination, despite the fact that its urban areas are at especially high risk for yellow fever outbreaks. The culmination of travelers returning to Houston from endemic areas, subtropical climate, high prevalence of Ae. aegypti mosquitoes, and areas of dense housing overlapped with poverty place Houston at risk for yellow fever emergence.

We need to seriously evaluate the risks of the major southern cities of the US, including Houston, but also New Orleans, Tampa, and Miami for their vulnerability to Aedes-transmitted arbovirus infections, such as yellow fever. As we have pointed out, cities such as Houston have emerged as important endemic zones for neglected tropical diseases. While we are aware that US urban areas may not be as vulnerable to yellow fever as Memphis was more than a century ago, there is still an important risk that needs to be considered as part of our national emergency preparedness, particularly in light of an emerging dengue problem (i.e., another Ae. Aegypti mosquito transmitted virus infection) in Houston and other southern coastal US areas.

Sudan Reports Widespread Yellow Fever Outbreak, 14 Dead

December 4, 2013

Sudan’s Federal Ministry of Health (FMOH) has notified the World Health Organization (WHO) of an outbreak ofyellow fever that is affecting 12 localities in West and South Kordofan states.

A total of 44 suspected cases and 14 deaths have been reported from October 3 to November 24, 2013 in the localities of Lagawa, Kailak, Muglad and Abyei in West Kordofan and Elreef Alshargi, Abu Gibaiha, Ghadir, Habila, Kadugli, Altadamon, Talodi and Aliri in South Kordofan.

Field investigations carried out by the FMOH revealed that the initial suspected cases were reported among seasonal workers coming from the eastern states of Sudan who had traveled to West Kordofan for work in October. Subsequent cases were reported among locals in both West and South Kordofan states, following the arrival of the workers.

Blood samples that were collected during the field investigation tested positive for Yellow Fever by IgM ELISA Assay at the National Public Health Laboratory of the FMOH in Khartoum. The samples were retested at theInstitute of Pasteur in Senegal and were confirmed to be that of Yellow Fever. Subsequent seroneutralizing (PRNT) testing by WHO researchers also confirmed presence of yellow fever.

The field investigation also found evidence of Aedes aegepty mosquitoes in the areas where the infected persons were found. A. aegepty is one vector that can sustain transmission of yellow fever.

WHO is assisting the FMOH to strengthen surveillance efforts and to conduct active case searches in and around the region. So far no suspected cases have been reported from any of the areas outside of where the initial outbreak occurred. The FMOH is now organizing a massive vaccination program against yellow fever in the affected areas to prevent further infection.

According to a WHO report, it is estimated that yellow fever infects between 840,000 and 1.7 million people in Africa each year, resulting in about 29,000 to 60,000 deaths.

An outbreak last year in the Darfur region of Sudan resulted in 849 suspected cases and 171 deaths. Around five million people were vaccinated against yellow fever in the five states of Darfur following the outbreak. In 2005, a yellow fever outbreak was also reported from the South Kordofan state, resulting in 615 suspected cases and 183 deaths. A vaccination campaign followed targeting about 1.6 million people in the region.

Yellow fever, also known as Yellow Jack, is an acute viral hemorrhagic virus that affects 20 percent of an area’s population where it is commonly found. Most cases only cause a mild infection with fever, headache, chills, back pain, loss of appetite, nausea and vomiting. In these cases, the infection generally lasts three or four days.

In about 15 percent of cases, sufferers can enter a toxic phase of the disease with recurring fever accompanied by jaundice due to liver damage and abdominal pain. Bleeding in the mouth, eyes and gastrointestinal tract is also common at this stage and vomit may contain blood. This toxic phase is lethal in about 20 percent of cases, making the overall mortality rate for the disease about three percent. In severe epidemic outbreaks, mortality may rise to 50 percent or more.

For those who survive their infection, they usually do so without any organ damage and they are provided with a lifelong immunity to the virus.

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Yellow Fever immunization receives support from GAVI Alliance in Nigeria

he GAVI Alliance announced on Tuesday that it would support Nigeria’s first new national campaign against yellow fever in close to three decades.

The campaign will protect up to 60 million people by targeting individuals between the ages of nine months and 45 years. The new campaign to administer lifelong protection against the deadly disease will last three years.

“Vaccination is the most effective preventive measure against yellow fever,” Seth Berkley, the CEO of the GAVI Alliance, said. “Many millions of Nigerians who are currently vulnerable to this disease will receive lifelong protection against its potentially fatal effects.”

Nigeria is the last of the 13 highest-risk Central and West African countries to conduct a yellow fever campaign. In 2012, the World Health Organization and UNICEF estimated that just 25 percent of the six million children born each year in Nigeria received yellow fever vaccines as part of a routine infant package.

Yellow fever is still a significant issue in the region, due to high cross-border transmission and increased contact between humans and infected mosquitoes.

“Recent yellow fever outbreaks in Nigeria’s neighboring and nearby countries is a cause for serious concern,” Berkley said. “The resurgence of this disease puts millions of lives at risk, especially in towns and cities where large and uncontrollable outbreaks are more likely.”

There are an estimated 200,000 cases of yellow fever each year. The disease kills 30,000 people annually.

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In 1792 they set off to undo slavery but ended up sending yellow fever across the Atlantic

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Pandemic

A tale of unintended consequences

‘Ship of Death: A Voyage that Changed the Atlantic World’ by Billy G. Smith

The sad irony is that the Hankey set sail from England in 1792 on the noblest of missions.

The ship’s abolitionist passengers hoped to create an inspirational colony on an island off the west coast of Africa where Africans would be employees rather than slaves. “If we succeed, it promises happiness to millions of living and millions of unborn people,” wrote Philip Beaver, a leader of the expedition.

Instead, as Billy G. Smith recounts, the pioneers fueled one of the most devastating plagues in Western history. The colonists toted water to their ship from streams on the African mainland, not knowing that the mosquitoes that bred in the water carried yellow fever.

When the cargo ship sailed off on further ventures, crisscrossing the Atlantic for six months, it brought yellow fever to dozens of ports in the West Indies, North America and Europe. Other ships had carried yellow fever, but not with such lethality: “Until the Hankey’s voyage in 1793, the concatenation of conditions that was to detonate the yellow fever bomb had never been present in so many places at the same time and with such ferocity,” Smith writes. “The result was a pandemic that killed hundreds of thousands people.”

The Hankey, infamous in its own time, fell into obscurity within decades. Apparently by chance, Smith, a historian at Montana State University, came across references to the ship in shipping records in Philadelphia, where the epidemic killed one of every 10 residents. He tracked the ship’s voyages, matching them with yellow fever reports, and created a narrative that, the author says, “brings together peoples who lived thousands of miles apart who discovered . . . that far-distant events could have impacts, sometimes fatal, on their own lives.” It’s an apt lesson, he points out, for our ever-shrinking globe.