Yellow Fever

By: KK Porter

General Overview

History:

1648: Quarantine in Boston

1699: Yellow Fever in the American Colonies

1732: Death brings silence

1747: Philadelphia avoids an outbreak

1793: Yellow Fever decimates Philadelphia

1794: New York doctor makes an important observation

1799: Philadelphia Lazaretto is built

1878: Yellow Fever cripples the Mississippi Valley

08/14/1881: Carlos Finlay identifies a suspect

1897: Bacterium mistakely blamed for yellow fever

1899: Yellow Fever plagues Panama Canal workers

1900: U.S. Army researchers discover the causes of yellow fever

1901: Mosquito control efforts reduce disease cases

1904: Anti-mosquito methods allow completion of Panama Canal

1905: North America sees last yellow fever epidemic

1915: Rockefeller Foundation's yellow fever comission forms

1918: Anti-mosquito methods control yellow fever in ecuador

1930: Max Theiler takes on yellow fever

1931: Steps taken toward a vaccine

1936: Max Theiler devlops yellow fever vaccine

1951: Theiler wins Nobel Prize

1964: Major U.S. anti-mosquito measures begin

1970: Yellow fever mosquito reappears in South America

10/04/1999: Imported yellow fever cases lead to American deaths

2010: Yellow fever vaccination efforts continue


What part of the body does it affect:

Yellow fever affects the liver, causing yellowing of the skin, with possible damage to the central nervous system and the renel system including the kidneys.


How does the disease affect the body:


In mild cases the symptoms are similar to the flu, but serious cases develop a high temperature and may have a series of after effects, such as internal bleeding, kidney failure and meningitis. A classic feature of yellow fever is hepatitis, which is the reason for the yellow colouring of the skin (juandice) and the name of the disease.

Causes

How is the disease transmitted?

Yellow fever virus is transmitted to humans primarily through the bite of infected Aedes or Haemagogus species mosquitoes. Mosquitoes acquire the virus by feeding on infected primates (human or non-human) and then can transmit the virus to other primates (human or non-human). Humans infected with yellow fever virus are infectious to mosquitoes shortly before the onset of fever and for 3–5 days after onset.

Yellow fever virus has three transmission cycles: jungle (sylvatic), inter­mediate (savannah), and urban.

  • The jungle (sylvatic) cycle involves transmission of the virus between nonhuman 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.

Incidence

There's an increasing number of epidemics, in which a large number of people suddenly develop yellow fever.

Every year about 200,000 cases of yellow fever are recorded, and 30,000 of these die, but the figures are underestimated because of poor record-keeping.

In total, yellow fever occurs in 32 countries and more than 600 million people are at risk of catching the disease.

Yellow fever can cause sudden epidemics, with a mortality rate of almost 50 per cent. Although a safe, efficient vaccine has been available for the last 60 years, epidemics still occur, constituting a health risk in tropical regions.

The CDC has identified 45 counties with a risk of yellow fever transmission, many of them with tropical climates. While the actual number of yellow fever cases among U.S. and European travelers to these at-risk countries is low, vaccination is advised for most international travelers to these countries, since yellow fever has no cure and can be deadly.

Signs and Symptoms

The yellowing occurs because the disease causes liver damage, hepatitis. For some people, yellow fever has no initial symptoms, while for others, the first symptoms appear from three to six days after exposure to the virus from a mosquito bite.

An infection with yellow fever typically has three phases. The first phase of symptoms can last for three to four days and then, for most people, disappears. The first phase is generally non-specific and can not be distinguished from other viral infections.

The initial symptoms of yellow fever are:

  • Fever and chills
  • Flu-like symptoms such as muscle aches, headache, and vomiting.

The next phase is remission, which lasts for 48 hours. Patients improve. The majority recover.

Unfortunately, a third, more toxic phase of infection occurs for 15% of patients. Ultimately, a condition called viral hemorrhagic fever can develop, with internal bleeding (hemorrhaging), high fever, and damage to the liver, kidneys, and circulatory system. The World Health Organization estimates that up to 50% of people worldwide who reach this severe phase of infection die, while half recover.

The third-phase symptoms of yellow fever are:

  • Jaundice (liver damage), which causes yellowing of the skin and eyes
  • Hepatitis (inflammation of the liver)
  • Internal bleeding (hemorrhaging)
  • Vomiting blood
  • Shock
  • Multisystem organ failure leading to death

Diagnosis

Yellow fever is diagnosed by your symptoms, recent travel activity, and blood tests. Yellow fever symptoms can mimic symptoms of other tropical disease such as malaria and typhoid, so it is definitely important to see a doctor to determine your diagnosis.

Treatment

Since there is no cure for the viral infection itself, medical treatment of yellow fever focuses on easing symptoms such as fever, muscle pain, and dehydration. Because of the risk of internal bleeding, avoid aspirin and other nonsteroidal anti-inflammatory drugs if you suspect you have yellow fever. Hospitalization is often needed.

Prevention

Because there is no cure for yellow fever, prevention is critical. The yellow fever vaccine is advised for adults and children over age 9 months who are traveling to or living in countries with a known risk of yellow fever. Certain countries in Africa and Latin America with the highest risk of exposure to yellow fever now require proof of yellow fever vaccination before allowing you to travel there.

Travel medicine clinics and state or local health departments usually offer the vaccine, which needs to be repeated every 10 years for people traveling to high-risk areas. These approved vaccination centers also provide you with the International Certificate of Vaccination that you'll need to enter certain at-risk countries.

Fun Facts

  • Sometimes called the yellow jack or black vomit
  • The United States has made attempts to eliminate this mosquito but has not been successful yet.

  • These mosquitoes may lay their eggs in the same containers where other mosquito species have laid their eggs.

  • The Aedes aegytpi is particularly fond of human ankles when it is searching for a good spot to bite a human.

  • If you open a cupboard and mosquitoes fly out, then you may have Aedes aegypti mosquitoes in your kitchen. In regions with the yellow fever mosquito, it is not unusual to open a cupboard or cabinet and find an adult Aedes aegypti mosquito resting inside.
  • This mosquito stays close to its breeding site, typically traveling only a few hundred yards away.

Big image

The mosquito that gives you yellow fever above