Between the College's advisory on August 25 and the death of Dr. Hutchinson from yellow fever on September 7, panic spread throughout the city; more people fled. Between August 1 and September 7, 456 people died in the city. On September 8, 42 deaths were reported.[18] An estimated 20,000 people left the city through September, including national leaders.[9] The daily death to

l remained above 30 until October 26. The worst 7-day period was between October 7 and 13, when 711 deaths were reported.[18]

We know today that yellow fever is a virus spread by the Aedes aegypti mosquito. This mosquito has peculiar habits which we are continuing to learn about. Its most distinguishing feature from other mosquitoes is its preference for urban habitat. It breeds best in relatively clean standing water and cisterns were a prominent feature among many city houses in that day before indoor plumbing. It also feeds during the day, and so must have quite enjoyed the bustling scenes common at the quays of the major port cities of the 18th century. Finally, it has no trouble adapting to life inside a house. Thus in a day when window screens were unknown, it had ready access to relatively protected environments.

No one would ever know precisely how many Philadelphians died of yellow fever in 1793. What was clear to all was that life would never be the same. Changes also came to the city because of the fever. Efforts were made to keep the markets and streets free of offensive-smelling matter, and the laws holding homeowners responsible for cleaning up their property were strengthened. The biggest improvement was made in the way water was supplied to Philadelphia. Water from the system – the first water system in the United States – was sweeter tasting and had no offensive odor. Plus the water flowed with enough force to hose streets and docks clean and to flush open clogged sewers. Eliminating the backbreaking need to hand-pump every drop of water had another beneficial effect as well. People began to bathe more often. Everyone – even those who had run from the city – considered himself or herself a survivor. They were a people left scarred, emotionally and physically. Sudden, mass death had stricken their city, and they were no wiser at all about the nature of the killer. They knew only one thing for certain: when next summer’s hot, humid weather returned, yellow fever might very well visit their homes again.

Yellow fever and the yellowfever mosquito are thought to have originated in Africa. It was brought to the New World on slave ships in the 1500s. Yellow fever ravaged Europeans in the New World. Buckley (1985) stated, "The West Indies was, quite simply, a deathtrap for whites without immunity to yellow fever." The British were repeatedly stung by the disease in the Caribbean and South America. In 1741, during an expedition to capture Peru and Mexico, British forces were reduced from 27,000 to 7,000 by the dreaded disease they called "black vomit." Coastal towns and hamlets in the United States were particularly vulnerable to the disease in the seventeenth and eighteenth centuries. Even as late as 1878, a yellow fever epidemic struck more than 100 United States towns, killing at least 20,000 people.

Several mild problems have been reported within 2 weeks of getting the vaccine: headaches, upper respiratory tract infection (about 1 person in 3) stuffy nose, sore throat, joint pain (about 1 person in 6) abdominal pain, cough, nausea (about 1 person in 7) diarrhea (about 1 person in 10) fever (about 1 person in 100)

Sylvatic yellow fever (also known as “jungle yellow fever”) occurs when the disease is passed from monkeys infected by wild mosquitoes to humans. Intermediate yellow fever—the most common type of outbreak in modern Africa—results when semi-domestic mosquitoes (which can infect both monkeys and humans) are present in an area where they commonly come into contact with humans. Urban yellow fever occurs when the Aedes aegypti species of domestic mosquito transmits the virus between humans, without transmission via other primates.

African Americans played a vital role in the epidemic of 1793. Rush pleaded for the help of Philadelphia’s free black community, believing that African Americans were immune to the disease. African Americans worked tirelessly with the sick and dying as nurses, cart drivers, coffin makers, and grave diggers. Absalom Jones and Richard Allen, religious leaders who would later go on to found the first black churches of Philadelphia, African Episcopal Church of St. Thomas, and African Methodist Episcopal Church, respectively, described their experience as volunteers in 1793: “at this time the dread that prevailed over people’s minds was so general, that it was a rare instance to see one neighbor visit another, and even friends when they met in the streets were afraid of each other, much less would they admit into their houses.” This was not the only horror that Absalom Jones and Richard Allen observed. They observed horrendous behavior from the fearful citizens of Philadelphia: “[Many white people]…have acted in a manner that would make humanity shudder.” Despite Dr. Rush’s theory, 240 African Americans died of Yellow Fever.

The first major American yellow fever epidemic hit Philadelphia in July 1793 and peaked during the first weeks of October. Philadelphia, then the nation’s capital, was the most cosmopolitan city in the United States. Two thousand free blacks lived there, as well as many recent white French-speaking arrivals from the colony of Santo Domingo, who were fleeing from a slave rebellion. Major Revolutionary political figures lived there, and in the first week of September, Thomas Jefferson wrote to James Madison that everyone who could escape the city was doing so. The epidemic depopulated Philadelphia: 5,000 out of a population of 45,000 died, and chronicler Mathew Carey estimated that another 17,000 fled.

Western Africa has long been regarded as the home of yellow fever, although the first recorded outbreaks of the disease were in central and coastal South America after the Spanish conquest in the 16th century. For the next 300 years, yellow fever, given various names such as Yellow Jack and “the saffron scourge,” was one of the great plagues of the New World. The tropical and subtropical regions of the Americas were subjected to devastating epidemics, and serious outbreaks occurred as far north as Philadelphia, New York, and Boston but also as far away from the endemic centres as Spain, France, England, and Italy.

Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes. The "yellow" in the name refers to the jaundice that affects some patients. Up to 50% of severely affected persons without treatment will die from yellow fever. There are an estimated 200 000 cases of yellow fever, causing 30 000 deaths, worldwide each year, with 90% occurring in Africa. The virus is endemic in tropical areas of Africa and Latin America, with a combined population of over 900 million people. The number of yellow fever cases has increased over the past two decades due to declining population immunity to infection, deforestation, urbanization, population movements and climate change. There is no specific treatment for yellow fever. Treatment is symptomatic, aimed at reducing the symptoms for the comfort of the patient. Vaccination is the most important preventive measure against yellow fever. The vaccine is safe, affordable and highly effective, and 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. The vaccine provides effective immunity within 30 days for 99% of persons vaccinated.

WHO response WHO is the Secretariat for the International Coordinating Group for Yellow Fever Vaccine Provision (ICG). The ICG maintains an emergency stockpile of yellow fever vaccines to ensure rapid response to outbreaks in high risk countries. The Yellow Fever Initiative is a preventive control strategy of vaccination led by WHO and supported by UNICEF and National Governments, with a particular focus on most high endemic countries in Africa where the disease is most prominent. The Initiative recommends including yellow fever vaccines in routine infant immunizations (starting at age 9 months), implementing mass vaccination campaigns in high-risk areas for people in all age groups aged 9 months and older, and maintaining surveillance and outbreak response capacity. Between 2007 and 2012, 12 countries have completed preventive yellow fever vaccination campaigns: Benin, Burkina Faso, Cameroon, Central African Republic, Côte d’Ivoire, Ghana, Guinea, Liberia, Mali, Senegal, Sierra Leone and Togo. The Yellow Fever Initiative is financially supported by the GAVI Alliance, the European Community Humanitarian Office (ECHO), the Central Emergency Response Fund (CERF), the Ministries of Health, and the country-level partners.

There is no cure for yellow fever. Antibiotic drugs that can be used to treat other diseases do not stop yellow fever because they do not work against viruses. Treatment involves easing the patient’s symptoms with pain medication and fluids. Severe symptoms usually require treatment in a hospital.