Yellow Fever – One Injection, 10 Years’ Protection

Introduction:

Traveling to a foreign country can be exciting, even for the most experienced travelers. Unfamiliar conditions and diseases can cause nervousness and fear.

Research is a key component before leaving for a trip. Travelers should ask: “Do I have everything I need?” This question covers more than just the obvious items of clothing or prescriptions. Many individuals forget the importance travel health can play. Vaccinations and other preventative measures are necessary to help stay healthy while away.

Vaccines or other preventative measures may seem to expensive or unnecessary. But, exposure to a deadly disease like yellow fever could ruin a well planned trip.

What is Yellow Fever?
How Does Yellow Fever Spread?
The History of Yellow Fever Outbreaks
Yellow Fever in the United States
History of the Yellow Fever Vaccine:
Is the Yellow Fever Vaccine Safe?
Where is Yellow Fever Found?
How Big of a Risk Is Yellow Fever?
Where Have Yellow Fever Outbreaks Occured?
Why is Vaccination Important?
Is The Yellow Fever Vaccine Worth The Cost?

What is Yellow Fever?

Yellow fever is a mosquito-borne disease that is not well known in the North America. But around the world, this disease is a notorious killer. It is so common that some nations require travelers receive the vaccine before coming. With one injection, travelers can guarantee themselves 10 years of protection from yellow fever.

Yellow fever is a viral disease related to West Nile virus and Japanese encephalitis. Those infected often recover with serious complications. The virus usually causes fever, body aches, and general feelings of malaise. [1]. But, for a certain percentage yellow fever can have deadly repercussions.

Symptoms develop three to six days after infection. Up to 15 percent of those infected will experience initial symptoms. After a time, they receive an onslaught of toxicity to the entire body. Patients develop severe symptoms that can lead to liver and kidney damage. Other symptoms include bleeding from mucous membranes and orifices, vomiting curdled blood and shock. Up to 50 percent of those with severe yellow fever disease die. Those who recover from yellow fever infection may deal with lifelong complications.[2]

How Does Yellow Fever Spread?

The yellow fever virus infects people through the Aedes or Haemagogus species mosquitoes. The mosquitoes get the virus from biting infected primates then spread it through bites. Per the CDC, a person infected by mosquitoes carrying the virus may not see any symptoms for three to six days. The infected person may be home from his or her trip to the at-risk country before they even feel ill.

Yellow fever transmission follows cycles related to the ecology and environment of the area. These include the jungle (sylvatic), intermediate (savannah), and urban cycles.

In the jungle cycle, transmission of the virus occurs between primates and mosquitoes. The virus is then transmitted to people who work in or visit the jungle.

The intermediate cycle involves transmission from mosquitoes to humans living in outside the jungle. These individuals often live in the grasslands circling the jungle climate. Viral transmission takes many forms here, including mosquito to human and monkey to mosquito.

The urban cycle, is from an infected person returning to urban areas. These individuals become infected while working or traveling in the jungle or savannah. A local mosquito bites the infected person and spreads the disease in urban areas [3].

The History of Yellow Fever Outbreaks:

Yellow fever is a significant health concern in many tropical and subtropical regions. Its impact has even affected history.

One of the first outbreaks was recorded by the explorer Christopher Columbus. In 1495, during his voyage from Spain to the Americas, Columbus came in contact with the disease. After the Spanish defeated the natives, they experienced a yellow fever epidemic. The virus prompted Columbus and his men to change location [4]. Throughout history ships were often linked to spreading yellow fever. These ships were called “yellow jacks” for the flags they would display when someone on board had the disease.

In 1649, Cuba suffered an epidemic which killed one-third of the residents of Havana. Then, from 1856 to 1879 the disease struck almost monthly, in the country. [5].

Between 1895 and 1898, 16,000 Spanish soldiers died from yellow fever. At the start of the Spanish-American War, only a quarter of Spanish soldiers were healthy enough to fight. During this war, more U.S. soldiers died as a result of yellow fever than due to the war itself.

During the 1700s to 1800s, yellow fever was a feared contagion throughout the western hemisphere. The medical community at the time did not know exactly what caused yellow fever. But, it did know the virus was endemic and epidemic, was caused by a ‘germ’ and occured in trade ports. As bacteriology and scientific techniques improved, efforts at vaccine development progressed. By 1900, there had been little significant progress in yellow fever prevention [6].

Yellow Fever in the United States:

In Philadelphia in 1793, and estimated 10 percent of citizens died from yellow fever. Many residents, including Thomas Jefferson, George Washington, escaped the disease by fleeing the city.

Yellow fever outbreaks continued in the United States. By 1878 the disease had begun to spread to New Orleans to where thousands of Cuban refugees had fled. Foreigners, the shipping industry, and returning soldiers resulted in the Quarantine Act of 1878. This act empowered the Marine Hospital Service to stop disease spread by sailors. Violations of the law helped yellow fever spread through the Mississippi Valley.

Half of Memphis’s residents fled to more rural areas as far away as Indiana, Illinois and Ohio. Some areas welcomed them, and others turned them away with “shotgun barricades.”

Mosquitoes were finally pinpointed as the transmission source in 1900. But, the last yellow fever epidemic in the U.S. was five years later, in New Orleans. This outbreak resulted in 100 yellow fever cases and it was attributed to a smuggler’s ship and its banana crop.

Yellow fever has been a devastating force throughout world and U.S. history. The historical toll of yellow fever outbreaks is significant. This “rare” disease has killed more US citizens than some wars.

History of the Yellow Fever Vaccine:

After the Spanish-American War, concerns developed about endemic yellow fever in Cuba. U.S. Surgeon General Walter Reed found measures taken in Havana had not stopped the virus. He also determined mosquitoes were to blame for the spread of the disease [6].

After filtering samples of infected material, Reed found yellow fever wasn’t bacterial. A Havana physician attempted to immunize patients but found many of the subjects became ill. Attempts to create a vaccine ended there.

Yellow fever was especially known for the waxing and waning of infections. A new settlement, the rainy season or an increase in the population would cause new outbreaks. Early in the 1900s, scientists discovered the Aedes aegypti mosquito transmits of the disease. Yellow fever prevention then focused on reducing the population size of mosquitoes.

In 1937, researchers developed a yellow fever vaccine. The vaccine was safe, effective and inexpensive. It was ideal for mass vaccination campaigns. Around the world, medical workers and physicians initiated mass vaccination campaigns beginning in 1940.

These campaigns were a success. Outbreaks disappeared, and people began to forget about yellow fever. The disease still exists in isolated pockets among smaller populations of people and mosquitoes. People had let down their guard with vector control and vaccination. Meanwhile, a new generation of non-immune and -immunized children was born.

The vaccines in use today use the same strains as more than 70 years ago. Today, there are several vaccination campaigns against yellow fever. The GAVI Alliance aims to eradicate yellow fever in 12 countries in west and central Africa. UNICEF provides the vaccine, and the World Health Organization handles logistics. This vaccination campaign focuses on many of Africa’s largest cities. The GAVI Alliance reports more than 70 million people received the yellow fever vaccine [7].

The current yellow fever vaccine is a live, attenuated (weakened) virus. The vaccine is one shot and offers protection for up to 10 years [8]. At-risk people should get a booster shot every 10 years to stay protected against the disease. Recipients also receive the International Certificate of Vaccination or Prophylaxis or ‘yellow card’. Certain countries require this card for entry. Travelers without a card may have to receive a vaccination upon entry. Or, they may be detained for up to six days to prove they are not infected with yellow fever.

The CDC recommends vaccination for the following groups:

• Anyone nine months to 59 years-old who is traveling to a country requiring vaccination
• Visitors to countries where yellow fever is endemic
• Laboratory and medical personnel who could be exposed to the virus

After receiving the vaccine, recipients shouldn’t donate blood for 14 days as the virus can stay in the bloodstream.

Is the Yellow Fever Vaccine Safe?

Various studies have proven the efficacy of the yellow fever vaccine. All have shown the yellow fever vaccine to be safe and effective in preventing the virus.

Vaccination is the most important step in prevention. Yellow fever wareness, mosquito netting, and repellents also play a key role.

Where is Yellow Fever Found?

Yellow fever disease concentrated in South America and sub-Saharan Africa [9]. South and Central American countries where yellow fever is endemic include:

Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Trinidad, Tobago and Venezuela

Yellow fever is also endemic in these African countries:

Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Congo, Republic of the Côte d’Ivoire (Ivory Coast), Democratic Republic of the Congo, Equatorial Guinea, Ethiopia, Gabon, The Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Mali, Mauritania, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, Sudan, South Sudan, Togo, and Uganda.

Many of the countries in the endemic zone require proof of vaccination to enter the nation. These countries include:

Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Congo, Republic of the Côte d’Ivoire, Democratic Republic of Congo, French Guiana, Gabon, Ghana, Guinea-Bissau, Liberia, Mali, Niger, Rwanda, São Tomé and Príncipe, Sierra Leone and Togo, reports the Passport Health website [10].

How Big of a Risk Is Yellow Fever?

Yellow fever is a serious risk for travelers to areas where it is endemic. The exact level of risk varies based on an individual’s itinerary and vaccination status. Older travelers have an especially high risk of becoming ill. Vaccination for these individuals is highly recommended.

Risk of infection is highest July through October in West Africa. In South America, infection rates are highest between January and May.

Where Have Yellow Fever Outbreaks Occured?

The threat of urban outbreaks is real and significant in many African cities. Even one case of yellow fever within a major city can set off a widespread epidemic of illness.

• 1960: Ethiopia- 100,000 people infected, and 30,000 dead from an urban outbreak.
• 1983: Ghana and Burkina Faso- an urban outbreak killed 80 percent of those infected
• 1992: Kenya- first outbreak of yellow fever in 49 years.
• 1996: Benin- first outbreak in 55 years. The chain of transmission between people lasted for more than eight months.
• 2001 & 2002: Cote d’Ivoire and Senegal suffered their first urban outbreaks

Yellow fever is not just a risk factor for travelers planning a safari or a trek through the jungle. The disease is a concern for business travelers who spend their time urban areas.

From 1970 through 2011, nine un-vaccinated travelers contracted yellow fever. Eight of those nine people died. An un-vaccinated traveler in an endemic region for two-weeks will face an infection risk.

• West Africa has 50 infections per 100,000 population and 10 deaths per 100,000 population.
• South America has five infections per 100,000 population and one death per 100,000 population.

Note that these statistics reflect infection prevalence in the native population. Travelers actually face a higher risk of infection than locals.

The actual risk level for travelers depends on whether the traveler takes anti-mosquito precautions. This includes:

• Using mosquito repellent
• Wearing long pants and long-sleeved shirts
• Using mosquito netting
• Staying in dwellings with window screens
• Limiting outdoor exposure
• Avoiding exposure to infected primates
• Receiving a yellow fever vaccine

The risk to travelers is much higher than natives due to herd immunity. Indeed, members of the local population may have had a case of yellow fever in the past, so they are now immune. Travelers to South and Central America are at a greater risk of contracting the virus due to mosquito patterns.

Each year, 200,000 people contract yellow fever, and 30,000 of those people die. When an epidemic occurs in an un-vaccinated population, the fatality rate of the disease ranges from 50 to 70 percent. No treatment beyond comfort measures is available.

Why is Vaccination Important?

Societal benefits:

Yellow fever vaccination reduced the burden of illness in the Americas and sub-Saharan Africa. Vaccination is key to reducing the burden of infectious disease. With mass vaccination campaigns, diseases like yellow fever can be eliminated in local areas. Longterm mass vaccination campaigns help end the disease in communities. Vaccination is especially important when vector eradication is impossible. It is not possible to rid the environment of mosquitoes, but vaccination will help.

There are many societal benefits to yellow fever vaccination. Vaccination can reduce the burden to national health care systems. It also reduces social concerns like loss of household income and premature death. Vaccination also makes it less likely a person progresses to the severe stages of the disease. Herd immunity is also an important result of mass vaccination of yellow fever.

Herd immunity protects those who cannot receive the vaccine like babies ore the elderly. When a community is vaccinated, there is less inequality due to illness and lost income. Vaccination can extend life expectancy and safeguard pregnant women against pregnancy complications.

Benefits for Travelers:

Countries with yellow fever have many incomparable and enjoyable experiences to offer. Business travelers who have received the yellow fever vaccine will enjoy their personal time. This freedom is crucial during extended stays when there is even more free time. However they choose to spend their time, they will be able to enjoy it due to the security and peace of mind provided through vaccination. This peace of mind is priceless.

How should an individual go about obtaining a yellow fever vaccine? Those traveling to a yellow fever endemic country should visit a travel health specialist at least 10 days before travel. The CDC recommends travelers from 9 months to 59 years-old receive the vaccine. Just one shot confers protection against yellow fever for 10 years. The CDC also recommends a booster shot every 10 years for continued protection.

Besides vaccinating travelers, travel health specialists offer advice so individuals can better protect themselves. They consult on mosquito repellents, first aid supplies and other personal care products. After vaccination, travelers enjoy immunity against yellow fever for 10 years. This makes future travel convenient and less risky.

Is The Yellow Fever Vaccine Worth The Cost?

Financial and emotional costs far outweigh the cost of the yellow fever vaccine in the event of exposure.

From the standpoint of a business traveler, the benefits of vaccination are obvious. An hour visit with a travel health specialist is much more pleasant than illness. Proactive care also prevents lost work days on important assignments abroad.

Evacuation for serious illness can cost more than $100,000. Add this to the regular salary and loss of contributions the expense can be astronomical.

Avoiding unnecessary doctors’ visits or time in the hospital can save thousands of dollars. According to a study by the National Center for Health Statistics, the average cost of a visit to the emergency room is between $969 and $1062 [13]. One vaccine can prevent incurring these large costs.

The average cost of a travel consultation and vaccinations, including yellow fever, is $400. This is a fraction of the potential costs of exposure. The value and comfort found in the peace of mind for the traveler and their employer is free of charge.

One injection guarantees yourself or your traveling employee population 10 years’ of protection.