Essay: Is yellow fever becoming the latest global health emergency?

Introduction and History
The origin of yellow fever starts in Africa, as a result of transmission of infection from primates to humans. Studied suggest that the disease began on the coast of Africa yet spread to Central and West Africa as a result of the growing epidemic. Natives of Africa were not as affected as were travelers or Europeans. It is thought that over time, natives acquired immunity to the infection as a result of prolonged exposure as a kid. In 1647, the first known outbreak of yellow fever was recorded in Barbados, following another outbreak in Brazil in 1685. Yellow fever was nameless for the first hundred years of the epidemic, until it was nicknamed “yellow fever” as a result of the symptoms showed on its host.“Possibly as early as the sixteenth century, the virus and its mosquito vector were transported on ships sailing from West Africa to the West Indies. Later, due to transport by coastal shipping of both the vector and infected humans, yellow fever virus was carried to and ravaged much of the eastern regions of the Americas”(Clements, Harbach 2017). “Outbreaks of Yellow Fever seemed to occur more often in southern climates, and especially in those with high humidity and large quantities of stagnant surface water,” however they did not especially exclude the United States (Thompson, O’Leary, 1996).
Global Epidemiology
The epidemic of yellow fever was originally thought to have been introduced into the Americans as a result of ships carrying slaves from West Africa. Due to prominent epidemics that started throughout the 18th and 19th century, American colonies had to refuse the entrance of ships that were arriving from infected areas. “Many opponents of slavery saw yellow fever as divine retribution for the United State’s involvement in the slave trade” (Chacon, 2014). It is not known if it is spread by person-to-person contagion or some element in the air or environment. There was no way to predict how it was going to spread or protect yourself from it. Symptoms usually did not appear for up to a week after the initial contagion, and by then you could have already come in contact.
Epidemiology in the United States
In the late years of the 19th century the United States had interest in Cuba due to their mass production of sugar, which can account for millions of annual income (Clements, Harbach, 2017). Cuba was a major port for trading, and the prime point of shipping products across the sea to the US. The transportation of coastal shipping can be at fault for the spread of infection. The first yellow fever epidemic in the United States occurred in 1693 in Boston when a ship brought the disease over from the Indies. Despite their port security methods to block infected areas, some ships passed claiming they were sterile. 100 years later, the epidemic made its way to Philadelphia, the former capital of the United States. It was carried over by French refugees who became infected at the slave rebellion in Haiti. Roughly, ten percent of the population died from yellow fever that year. Since there was no known vaccine or cure, many philadelphians fled the city, including President Washington.
“In 1878, infected passengers on steamships carrying yellow fever to New Orleans were allowed to disembark without passing through quarantine, and the yellow fever they carried was thought to have touched o the worst epidemic in U.S. history. roughout the summer, yellow fever ravaged the population of New Orleans and spread up the Mississippi Valley as far north as St. Louis, while also moving outward along the railroad lines. Outbreaks of yellow fever occurred in more than 100 cities and towns, over 120,000 people were infected and more than 20,000 died. e economic losses across the region were estimated to amount to $100 million, possibly more” (Clements, Harbach, 2017).
Once again trying to regulate the origin of yellow fever, “the U.S. sent a group of experts, the Havana Yellow Fever Commission, to Cuba to determine the sanitary conditions that allowed yellow fever to ourish in Cuban ports and to devise measures that might prevent ships bound for the U.S. from carrying the disease in any way” (Clements, Harbach, 2017).
“At the outbreak of the epidemic there was no city Board of Health in existence. The last board had been totally ineffective since it lacked sufficient authority to enforce its rules and regulations, and had been denied support by the city authorities” (Carrigan, 1853). No one was trained enough nor had been exposed to yellow fever enough to understand the specific cause and protection methods. People were left in the dark with the true severity of the infection and well as close by cases.
“When informed of the first cases of yellow fever that appear in summer, the newspaper press almost invariably denies the truth of the reports, and, not unfrequently, showers upon the heads of those whose duty it is to pronounce upon the character of the prevailing disease, volumes of abuse and ridicule. If the cases multiply and the sign of the times plainly indiare the approach of an epidemic, the able editors of our valuable daily journals, under what i must pronounce a most erroneous impression of their duty to the public, studiously endeavour to conceal or suppress the true state of affairs” (Fenner, 2008).
Newspapers were hesitant to release stories regarding yellow fever because businesses feared that word of an epidemic would cause a quarantine to be placed on the city and trade would suffer. In their defense, there was no trained physicians that could properly treat yellow fever so it became difficult to write a story solely based on guesses. “A cartoon posted in the Daily Item mocked the handling of fever cases in New Orleans by depicting sufferers from non-fever maladies, like a toothache and a broken arm, as yellow fever cases according to the Board of Health. By doing so, the newspaper vocalized its disapproval of the Louisiana Board of Health’s handling of fever cases and the medical knowledge of the board’s employed physicians” (Runge, 2013). People were aggravated with the lack of awareness and accuracy from journals, so they found comic relief in making fun of them.
“Journals began to comment on the pestilence, blaming the city council and its do-nothing policy. Under tremendous pressure from public opinion and urged on by the Mayer, the Council on july 25 finally appointed a Board of Health” (Carrigan, 1853).
Pathophysiology
“The phenomenon of yellow fever was like a jigsaw puzzle with a number of missing pieces. Until those pieces were discovered the picture remained distorted until the discovery of the insect vector, the irregular spread of the pestilence presented a knotty problem in logic to speculative minds” (Carrigan, 1853).
U.S Army surgeon Major Walter Reed made the first important contribution to the field of medicine with his study of yellow fever. During his time of service in the Spanish-American war, Reed found soldiers dying from both yellow fever and malaria. Unsure of the cause, Reed set out to appoint a commission to investigate the cause of the disease. “Known officially as the United States Army Yellow Fever Commission, it was known simply as the Reed Commission for Major Reed, who was the chairman of the four-man body that included three other specialists in infectious disease: James Carroll, Aristides Agramonte, and Jesse W. Lazear, all of whom were contract doctors for the Army.”[16] Carlos Finlay was a Cuban epidemiologist who had made many strides of discovering the origin of yellow fever in Cuba. The United States sought out Finlay
“The first methodical and scientific approach to the study of the mode of transmission of yellow fever was undertaken by Finlay after he had returned to Cuba. In a review article on yellow fever published in 1895, Finlay recalled that, in December 1880, a comparison of certain characteristics of yellow fever transmission with those needed for mosquito activity – such as the absence of both above a certain altitude and at low temperatures – led him to deduce that yellow fever could not be acquired by inhalation, ingestion or contact. He postulated that the mode of transmission might be by inoculation of disease germs by some piercing insect (algun insect puzzante) peculiar to yellow fever countries” (Clements, Harbach, 2017). By the 1900s, the Commission proved that yellow fever was not caused by person to person contact or poor sanitation but by female Aedes Aegypti mosquitoes which carried the virus person to person.
James Carroll, who also served on the yellow fever commission board argued the mosquito theory and proposed that volunteers must be exposed to the mosquitoes to prove the contraction. Carroll and Jesse William Lazear, another commission members, subjected themselves to the bite of the infected mosquitoes to test the theory proposed. Unfortunately, Lazear died but Carroll recovered and was able to finish a series of experiments. “They made a convincing demonstration of yellow fever transmission to human volunteers by the bite of infected Aedes aegypti. The control of the demonstrated vector brought yellow fever under control in the major port cities of the Old World and New World.It was thought, in the early decades of the twentieth century, that the disease could be vanquished” (Downs, 1982).
“Dr. Finlay, a Cuban who had been a member of the auxiliary Yellow Fever Commission, unfortunately made his demonstration in an era when many erroneous theories were strongly entrenched, and for years he was called the ‘mosquito maniac.’ During those years Matas alone supported Finaly’s hypothesis-which, of course, was correct as we know now” (Corndell, 1985).
Portal of Entry
Yellow fever virus is an RNA virus that belongs to the genus Flavivirus. It is related to West Nile, St. Louis encephalitis, and Japanese encephalitis viruses. Yellow fever virus is transmitted to people primarily through the bite of infected Aedes or Haemagogus species mosquitoes.
Aedes aegypti, the yellow fever mosquito originated in AFrica but can be found in tropical, temperate regions globally. Besides yellow fever, this mosquito is the vector for a majority of tropical fevers. Only female mosquitoes bites for blood, which is required for her eggs to mature. The lifespan of the Aedes is fairly short, lasting roughly two to four weeks. However, depending on the environment in which eggs were laid, they can remain viable for over a year. In the United States, the Aedes aegypti can be found throughout the southeast region but they are slowly declining due to competition with other mosquitoes.
Transmission
“Yellow fever virus has three transmission cycles: jungle (sylvatic), inter­mediate (savannah), and urban. The jungle (sylvatic) cycle involves transmission of the virus between non-human primates (e.g., monkeys) and mosquito species found in the forest canopy. The virus is transmitted by mosquitoes from monkeys to humans when humans are visiting or working in the jungle.In Africa, an intermediate (savannah) cycle exists that involves transmission of virus from mosquitoes to humans living or working in jungle border areas. In this cycle, the virus can be transmitted from monkey to human or from human to human via mosquitoes.The urban cycle involves trans­mission of the virus between humans and urban mosquitoes, primarily Aedes aegypti. The virus is usually brought to the urban setting by a viremic human who was infected in the jungle or savannah.” [19]
 
Clinical Manifestation
More than twenty percent of patients died after showing signs and symptoms of yellow fever. “After the bite of the infecting mosquito, it takes several days before symptoms appear” (Grunfeld, 2006). Due to the delay of symptoms, many of those infected spread the disease unknowing. “The disease characteristically began with high fevers, shaking chills that progressed to rigors, tachycardia, photophobia, conjunctival injection, petechiae, muscle pains, and headaches. The disease was punctuated by bleeding from the gums, epigastric discomfort, bilious vomiting, diarrhea, and melena. Jaundice, for which the disease was given its nickname “Yellow Jack,” subsequently developed. Following a respite, where symptoms abated, there would be an exacerbation of all previous symptoms plus bloody diarrhea, black-stained vomitus, coma, and death” (Thompson, O’Leary, 1996).
In the beginning of epidemic, physicians were unsure of treatment plans for early symptoms were mistaken for other diseases such as influenza. “The physicians knew not how to treat this uncommon disorder, which was suddenly caught and proved suddenly fatal. The calamity was so general, that few could grant assistance to their neighbors. So many funerals happening everyday, while so many lay sick, that white persons sufficient for burying the dead were scarcely to be found” (Simons, 1852). Unfortunately, yellow fever was a death sentence.
Treatment
“At the beginning of the twentieth century, there was no cure for yellow fever. The best that medical authorities could do was to quarantine the afflicted. Those quarantines usually waved the warning yellow flag, which gave the disease its colloquial name, “yellow jack” (Grunfeld, 2008). There were many poorly trained physicians who had no experiences with an infection of this magnitude.
“Popular therapies included bloodletting, blistering, cold water immersion, sweating, purging, and leeching. All of these were thought to be appropriate therapy for fevers. Fundamental to the treatment of Yellow Fever was calomel (Mercurous chloride) given in sufficient doses to induce vomiting and diarrhea. In smaller dosages, this agent acted as a laxative. At higher doses, the patients experienced symptoms of acute mercurial toxicity, which includes salivation, diarrhea, vomiting, and eventually neurologic damage. Because the patients treated with calomel were instructed to take the drug until salivation occurred, they undoubtedly experienced toxicity from the drug. Quinine, prescribed to reduce fever, was an appropriate treatment of malaria, but had little therapeutic efficacy in the treatment of Yellow Fever. Needless to say, the American physicians’ success rate in treating patients with Yellow Fever was poor” (Thompson, O’Leary, 1996).
 
Many members of the community came up with ways to prevent the mosquitoes from biting them. They urged citizens to screen windows to eliminate the threat of infection. They poured a layer of oil on cesspools and cisterns to kill mosquitoes and trapped those who were attracted to the decaying material. They suggested people to sleep under mosquito nets since mosquitoes are known to feast during dusk. Not complying with these rules resulted in a $25 fine, which equivalates to $680 in 2017 dollars, and 30 days in jail. “To be fair, not all sanitation and quarantine measures were total failures. Sanitation measures in fact helped remove some of the sewage issues in trade towns like New orleans and Memphis, which had provided excellent breeding ground for mosquitoes” (Runge, 2013).
There were numerous suggestions of treatments options that filled medical literature on a daily basis, however no explanation was proved to be plausible (Carrigan, 1853). Each doctor had their own experiences and conclusions, and refused to accept conflicting theories made by other physicians.
The first attempt to develop a vaccine for yellow fever was made by a Japanese bacteriologist. He successfully was able to isolate the disease and protect against it. He must have discovered out of luck because other scientists could not duplicate his vaccination and abandoned the theory. Years later, the bacterial strain was discovered by scientists at the Pasteur Institute. Unfortunately, the vaccination was known to cause neurologic complications and was only administered to willing patients. In 1937, hundreds of years after the first known outbreak of yellow fever, scientist Max Theiler was able to recreate the vaccination which was previously discovered. He noticed a mutation in the virus and was able to create a strain against it known as 17D. After years of trials, there was no severe complications as a resulting of becoming vaccinated. The 17D vaccine was globally disturbed and used efficiently.
Infection Prevention Policy
“The best way to reduce mosquitoes is to eliminate the places where the mosquito lays her eggs, like artificial containers that hold water in and around the home. Outdoors, clean water containers like pet and animal watering containers, flower planter dishes or cover water storage barrels. Look for standing water indoors such as in vases with fresh flowers and clean at least once a week.”[19] Limiting the places in which the female mosquitoes can lay their eggs while reduce the risk of them wanting to stay in that given area. The Center for Disease Control and Prevention also suggests using mosquito repellent that contain DEET[1]. In addition to repellent, the usage of long-sleeved shirts and pants will reduce surface exposure where the mosquitoes may prey.
Prognosis
“Although many countries have vaccination policies to prevent international spread of the yellow fever virus, implementation is inconsistent. Most, but not all countries where yellow fever is endemic require arriving international travellers without medical contraindications to provide medical documentation of vaccination as a prerequisite for entry. As the vaccine provides protective immunity to 90% and 99% of individuals 10 and 30 days after vaccination, respectively, most travellers are protected from acquiring and exporting the yellow fever virus. Furthermore, some countries where the disease is not endemic, but where the competent mosquito vector Aedes aegypti is present require travellers arriving from a yellow fever-endemic country to provide proof of vaccination” (Brent, Watts, 2018). While it is imposbbile to wipe out the infected mosquitoes population, we can provide protection to those who may encounter the risk of contraction. ”To account for the possibility that individuals infected with yellow fever virus within an endemic area might travel by land to a nearby airport in a non-endemic area, we used ArcGIS v. 10.4.1 to identify all commercial airports registered with the International Air Transport Association (IATA): (i) within 200 km of any yellow fever-endemic area worldwide (base scenario); and (ii) within 200 km of any city within a yellow fever-endemic area (urban scenario)” (Brent, Watts, 2018).
Luckily, there are few cases in which someone who received the vaccination still contracted the disease. “In 2016, the World Health Organization (WHO) concluded that a single dose of YF vaccine confers life- long immunity—thus, revaccination is no longer needed” [15]
Conclusion
Even though the states have been cleared, yellow fever outbreaks still exist in the world. “Evidence is mounting that the current outbreak of yellow fever is becoming the latest global health emergency, say two Georgetown University professors who call on the World Health Organization to convene an emergency committee under the International Health Regulations. In addition, with frequent emerging epidemics, they call for the creation of a “standing emergency committee” to be prepared for future health emergencies” (Staff, 2016). The latest outbreak in 2016 in Angola, suggests the Aedes Aegypti mosquito is still transmitting the disease as well as Zika and other viruses. Vaccine shortages and unavailability could be the factors in which strike a health crisis. Physicians are still confident in the worlds ability to combat the disease, yet some suggest we need to become more prepared in case an outbreak strikes unexpectedly. Currently, it is more likely to contract the disease on travels to other countries than the United States but nonetheless prevention is imperative. There is a only a limited barrier between agents and host, therefore other protective barriers must be set in place for extra protection, such as repellents, clothing choices and sanitation. The risk of another yellow fever outbreak is rare but not impossible.