Is yellow fever still around?

Many people who are traveling to warmer, more humid parts of the world where aedes mosquitos are rampant may wonder how prevalent yellow fever still is in the world.

Yes, yellow fever is still present in certain areas of the world. The disease is caused by a virus that is transmitted to humans through the bite of an infected mosquito. The mosquitoes that transmit the virus are found primarily in tropical and subtropical regions of Africa and South America.

Symptoms of yellow fever include fever, headache, muscle pain, nausea, vomiting, and jaundice (yellowing of the skin and eyes), which is where the disease gets its name. In severe cases, the disease can lead to liver and kidney failure, and even death.

There is a vaccine available to protect against yellow fever, and it is recommended for people who plan to travel to areas where the disease is present. Additionally, it is important to take steps to protect yourself from mosquito bites, such as using insect repellent and wearing long-sleeved shirts and pants.

However, yellow fever cases have been reported by WHO even in south east asia like Philippines, places that were considered free from yellow fever till recent times. As this a live attenuated vaccine, there are some restrictions and guidelines to follow before taking it.

It is advisable to check the Centers for Disease Control and Prevention (CDC) website or the World Health Organization (WHO) website for the most up-to-date information on yellow fever, including information on where the disease is present and vaccination recommendations.

Why hasn't yellow fever been stopped by the yellow fever vaccine?

Yellow fever has not been eradicated for a number of reasons. One of the main reasons is that the virus that causes the disease is maintained in a cycle between mosquitoes and monkeys in tropical and subtropical regions of Africa and South America, which makes it difficult to interrupt the transmission of the virus to humans.

Another reason is that the vaccines are not universally accessible to people living in the areas where the disease is prevalent, particularly in resource-limited settings.

Additionally, vaccine coverage is not 100% and the virus can continue to spread even among people who are vaccinated, which makes it difficult to achieve herd immunity and eradicate the disease.

Also, funding and infrastructure required for widespread vaccinations and mosquito control can be inadequate in some areas. This can be due to lack of political will and/or limited resources in some of the countries where the disease is prevalent.

Another possible reason for Yellow fever not being eradicated is that the live attenuated vaccine available is not as efficient as measles and polio vaccine, and also there are some risks associated with its usage.

Finally, as the yellow fever is an arbovirus which means its transmitted by mosquitoes, controlling the vector population is also a huge task.

Eradication of yellow fever is a complex and challenging process that requires sustained efforts to improve access to vaccines, strengthen disease surveillance and response, and implement effective mosquito control measures.

Could yellow fever spread in the U.S.?

There are at least three notable examples of yellow fever outbreaks that occurred in the U.S.:

1. The 1793 Philadelphia outbreak: This was one of the most severe yellow fever epidemics to occur in the United States. The disease arrived in Philadelphia, which was then the capital of the United States, via shipping from the West Indies. The outbreak resulted in the deaths of approximately 5,000 people, which was about 10% of the city's population at the time.
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3. The 1878 Memphis outbreak: This outbreak of yellow fever was one of the deadliest in American history, with an estimated 20,000 cases and 7,000 deaths. The disease spread quickly in Memphis due to the city's overcrowded and unsanitary conditions, and many residents fled in fear. The outbreak also led to a nationwide panic and severely damaged the city's economy.
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5. The 1905 New Orleans outbreak: This outbreak of yellow fever was the last major outbreak of the disease to occur in the United States. The outbreak began in the summer of 1905 and quickly spread through the city's densely populated neighborhoods. Despite efforts to control the outbreak, the disease ultimately resulted in over 6,000 cases and over 2,000 deaths.

It is possible for yellow fever to spread in the United States, but it would be highly unlikely. The mosquitoes that transmit the virus, Aedes aegypti and Aedes albopictus, are found primarily in tropical and subtropical regions of the world, and are not established in the continental United States.

The main way people contract yellow fever in the United States is through travel to areas where the disease is present and not being protected by the vaccine, and bringing the virus back with them. Cases imported from other countries would be identified by enhanced surveillance systems and public health interventions would be taken to prevent transmission in the U.S.

However, The Aedes mosquito species that can carry yellow fever, do have some presence in the U.S, such as A. aegypti, and A. albopictus. They are found in some southern states, mainly along the Gulf Coast, but populations have also been found in other states such as California, Arizona, and New York.

In case of a outbreak in nearby countries, it is possible that a few cases could occur in the U.S via travel, as the virus is present in Central and South America.

It's also important to note that the risk of yellow fever transmission in the U.S would depend on the local mosquito populations and their susceptibility to the virus, which is still poorly understood.

Overall, the risk of yellow fever transmission in the United States is currently considered to be low, but it's important to be aware of the disease and the risks associated with travel to areas where it is present.