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Yellow fever
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Yellow fever (also called yellow jack, or sometimes black vomit or American Plague) is an acute viral disease. It is an important cause of hemorrhagic illness in many African and South American countries despite existence of an effective vaccine. The yellow refers to the jaundice symptoms that affect some patients.
Yellow fever has been a source of several devastating epidemics.
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Encyclopedia
Yellow fever (also called yellow jack, or sometimes black vomit or American Plague) is an acute viral disease. It is an important cause of hemorrhagic illness in many African and South American countries despite existence of an effective vaccine. The yellow refers to the jaundice symptoms that affect some patients.
Yellow fever has been a source of several devastating epidemics. Yellow fever epidemics broke out in the 1700s in Italy, France, Spain, and England. 300,000 people are believed to have died from yellow fever in Spain during the 19th century. French soldiers were attacked by yellow fever during the 1802 Haitian Revolution; more than half of the army perished from the disease. Outbreaks followed by thousands of deaths occurred periodically in other Western Hemisphere locations until research, which included human volunteers (some of whom died), led to an understanding of the method of transmission to humans (primarily by mosquitos) and development of a vaccine and other preventive efforts in the early 20th century.
Despite the breakthrough research of Cuban physician Carlos Finlay, American physician Walter Reed, and many others over 100 years ago, unvaccinated populations in many developing nations in Africa and Central/South America continue to be at risk. , the World Health Organization (WHO) estimates that yellow fever causes 200,000 illnesses and 30,000 deaths every year in unvaccinated populations.
Pathogenesis
Yellow fever is caused by yellow fever virus, a flavivirus of the family Flaviviridae, a positive sense single-stranded RNA virus. Human infection begins after deposition of viral particles through the skin in infected arthropod saliva, hence it is considered an arbovirus. The mosquitos involved are Aedes simpsaloni, A. africanus, and A. aegypti in Africa, the Haemagogus genus in South America, and the Sabethes genus in France.
Yellow fever is frequently severe but moderate cases may occur as the result of previous infection by another flavivirus. After infection the virus first replicates locally, followed by transportation to the rest of the body via the lymphatic system. Following systemic lymphatic infection the virus proceeds to establish itself throughout organ systems, including the heart, kidneys, adrenal glands, and the parenchyma of the liver; high viral loads are also present in the blood. Necrotic masses (Councilman bodies) appear in the cytoplasm of hepatocytes.,
Yellow fever begins suddenly after an incubation period of three to five days in the human body. In mild cases only fever and headache may be present. Within 24 hours about 15% develop a more severe form, in which they enter the "toxic phase" characterized by fever, chills, bleeding into the skin, paradoxically slow heartbeat, headache, back pains, and extreme prostration. Nausea, vomiting, and constipation are common. Jaundice usually appears on the second or third day. After the third day the symptoms recede, only to return with increased severity in the final stage, during which there is a marked tendency to hemorrhage internally; the characteristic “coffee ground” vomitus contains blood. The patient then lapses into delirium and coma, followed by death in about 50% of those who enter the toxic phase. During epidemics a much higher proportion have entered the toxic phase, and the fatality rate has been as high as 85%. Although the disease still occurs, it is usually confined to sporadic outbreaks.
There is a difference between disease outbreaks in rural or forest areas ("jungle cycle") and in towns ("urban cycle"). Disease outbreaks in towns and non-native people may be more serious because of higher densities of mosquito vectors and higher population densities.
Prevention
In 1937, Max Theiler, working at the Rockefeller Foundation, developed a safe and highly efficacious vaccine for yellow fever that gives a ten-year or more immunity from the virus.
Treatment
There is no true cure for yellow fever, therefore vaccination is important. Treatment is symptomatic and supportive only. Fluid replacement, fighting hypotension and transfusion of blood derivates is generally needed only in severe cases. In cases that result in acute renal failure, dialysis may be necessary.
Current research
In the hamster model of yellow fever, early administration of the antiviral ribavirin is an effective early treatment of many pathological features of the disease. Ribavirin treatment during the first five days after virus infection improved survival rates, reduced tissue damage in target organs (liver and spleen), prevented hepatocellular steatosis, and normalized alanine aminotransferase (a liver damage marker) levels. The results of this study suggest that ribavirin may be effective in the early treatment of yellow fever, and that its mechanism of action in reducing liver pathology in yellow fever virus infection may be similar to that observed with ribavirin in the treatment of hepatitis C, a virus related to yellow fever. Because ribavirin had failed to improve survival in a virulent primate (rhesus) model of yellow fever infection, it had been previously discounted as a possible therapy.
Prognosis
Historical reports have claimed a mortality rate of between 1 in 17 (5.8%) and 1 in 3 (33%). CDC has claimed that case-fatality rates from severe disease range from 15% to more than 50%. The WHO factsheet on yellow fever, updated in 2001, states that 15% of patients enter a "toxic phase" and that half of that number die within ten to fourteen days, with the other half recovering.
History
Yellow fever has had an important role in the history of Africa, the Americas, Europe, and the Caribbean.
Europe: 541-549
Fragile after the fall of Rome, Europe was further weakened by "Yellow Plague" (yellow fever). The Byzantine Empire suffered as well.
Cuba: 1762-1763
British and American colonial troops died by the thousands in the British expedition against Cuba between 1762 and 1763. Epidemics struck coastal and island communities throughout the area during the next 140 years, with 10% of the population dying as a result.
Philadelphia, Pennsylvania: 1793
The Yellow Fever Epidemic of 1793 killed as many as 10,000 people in Philadelphia, Pennsylvania. Thousands, including President George Washington, fled the city, including most members of the Federal (Philadelphia was the capital of the United States at this time) and city governments. As a result, civil services collapsed and almost vanished. However, the mayor remained and eventually, with the help of a "Committee of Twenty" composed of volunteer residents drawn from all walks of life, order and civil services were restored.
The first family of Dolley Madison, neé Dolley Payne, who would later become First Lady of the United States during James Madison's administration, was stricken in this epidemic. John Todd, Dolley's husband, was a Quaker and a lawyer. He felt it was his duty to remain in Philadelphia and provide legal services (wills, probate, etc.) to those who were dying or the families of those who died. However, he moved his family across the river. One day on a visit to his family, he collapsed into his wife's arms on the doorstep of their house and died soon after. Dolley and her eldest son, John Payne Todd, contracted yellow fever but survived. Dolley's youngest son William Temple Todd and John's parents also perished in the 1793 epidemic. Alexander Hamilton and his wife, Elizabeth Schuyler, contracted yellow fever but survived.
Dr. Benjamin Rush also contracted yellow fever, but survived. His fame, as a signer of the Declaration of Independence and as head medical doctor for the American army in the middle Atlantic states region during the American Revolution, brought him hundreds, perhaps thousands, of patients during this epidemic. His methods were severe and split the medical community at that time, resulting in an ongoing letter-writing war in the press both during and after the epidemic. However, unlike a number of other doctors, he remained in Philadelphia and did his best to help the residents who were struck down by the disease.
Haiti: 1802
In 1802, an army of forty thousand sent by First Consul Napoleon Bonaparte of France to Haiti to suppress the Haitian Revolution was decimated by an epidemic of yellow fever (including the expedition's commander and Bonaparte's brother-in-law, Charles Leclerc). Some historians believe Haiti was to be a staging point for an invasion of the United States through Louisiana (then still under French control).
New Orleans, Louisiana: 1853
This outbreak claimed 7,849 residents of New Orleans. The press and the medical profession did not alert citizens of the outbreak until the middle of July, after over a thousand had already died. The reason for this silence was that the New Orleans business community feared that word of an epidemic would cause a quarantine to be placed on the city, and commerce would thus be hurt.
Norfolk, Virginia: 1855
A ship carrying persons infected with the virus arrived in Hampton Roads in southeastern Virginia in June 1855 . The disease spread quickly through the community, eventually killing over 3,000 people, mostly residents of Norfolk and Portsmouth. The Howard Association, a benevolent organization, was formed to help coordinate assistance in the form of funds, supplies, and medical professionals and volunteers which poured in from many other areas, particularly the Atlantic and Gulf Coast areas of the United States. See also The Mermaids and Yellow Jack: A NorFolktale a children's historical fiction written by Norfolk author Lisa Suhay, telling of the event and founding of the Bon Secours DePaul Hospital system in the United States in response to the epidemic.
Memphis, Tennessee: 1878
There were several outbreaks of yellow fever in Memphis during the 1870s, culminating in the devastating 1878 epidemic, with over 5,000 fatalities in the city itself and 20,000 along the whole of the Mississippi River Valley. It has been claimed that the large death toll was due to commercial interests taking precedence over reporting the outbreak of yellow fever.
The French Panama Canal Effort: 1882-1889
The French effort to build a Panama Canal was fatally damaged by the prevalence of endemic tropical diseases in the Isthmus. Although malaria was also a serious problem for the French canal builders, the numerous yellow fever fatalities and the fear they engendered made it difficult for the French company to retain sufficient technical staff to sustain the effort. Since the mode of transmission of the disease was unknown, the French response to the disease was limited to care of the sick. Unfortunately, the French hospitals contained many pools of stagnant water, such as basins underneath potted plants, in which mosquitoes could breed. The eventual failure, as a result of the deaths, of the French company licensed to build the canal resulted in a massive financial crisis in France.
Carlos Finlay and Walter Reed
Carlos Finlay, a Cuban doctor and scientist, first proposed proofs in 1881 that yellow fever is transmitted by mosquitoes rather than direct human contact. Walter Reed, M.D., (1851-1902) was an American Army surgeon who led a team that confirmed Finlay's theory. This risky but fruitful research work was done with human volunteers, including some of the medical personnel, such as Clara Maass and Walter Reed Medal winner surgeon Jesse William Lazear, who allowed themselves to be deliberately infected and died of the virus. Although Dr. Reed received much of the credit in history books for "beating" yellow fever, Reed himself credited Dr. Finlay with the discovery of the yellow fever vector, and thus how it might be controlled. Dr. Reed often cited Finlay's papers in his own articles and gave him credit for the discovery, even in his personal correspondence. The acceptance of Finlay's work was one of the most important and far-reaching effects of the Walter Reed Commission of 1900. Applying methods first suggested by Finlay, the elimination of yellow fever from Cuba was completed, as well as the completion of the Panama Canal. Lamentably, almost 20 years had passed before Reed and his Board began their efforts, twenty years during which most of the scientific community ignored Finlay's theory of mosquito transmission.
Finlay and Reed's work was put to the test for the first time in the United States when a yellow fever epidemic struck New Orleans in 1905, although efforts had been successful in Havana since 1901. A conference organized in New Orleans in 1905 by Dr. A. L. Metz resulted in President Roosevelt directing the United States' Government to take control of the matter. The United States Public Health Service put into effect a mosquito control campaign, this included, according to the PBS American Experience documentary The Great Fever, fumigating houses, inspecting cisterns for drinking water, and treating pools of standing water with kerosene. The result was that the death toll from the epidemic was much lower than that from previous yellow fever epidemics, and that there has not been a major outbreak of the disease in the United States since. Although no cure has yet been discovered, an effective vaccine has been developed, which can prevent and help people recover from the disease.
Use as a biological weapon
In the past, yellow fever has been researched by several countries as a potential biological weapon.
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