Yellow fever is a virus that is found tropical and subtropical areas such as South America or Africa (1). The virus is transmitted from person to person via mosquito (1). It however can’t be contracted through direct contact with someone infected (6). The virus normally spreads in the sylvatic cycle also known as the jungle cycle but if this gets into the Aedes mosquitos it can create a hard to contain urban version of the yellow fever (4). Most of the time it gets transmitted from monkey to monkey but rarely it can infect a human (4). Symptoms take 3-6 days to develop which can include fever, chills, headache, backache, and muscle ache (2). Approximately 15 percent of those who get yellow fever develop severe symptoms such as bleeding, shock, organ failure, and possibly death (2). Yellow fever has a large range of severity ranging from a febrile illness to a severe liver disease with bleeding (1). There is no actual treatment for the disease but there is a vaccination (1).
Yellow fever is cause by a 40nm to 50 nm wide enveloped RNA virus that is called Flavivirus (7). The flavavirus is 11,000 nucleotides long and has one open reading frame that encodes a polyprotein (7). The flavavirus infects monocytes, macrophages, and dendric cells as well as other things (7). The virus uses specific reptors to attach to the cells surface and gets taken up by the endosomal vesicle (7). When it gets inside the endosome it reduces the PH and causes the fusion of the endosomal membrane and the virus envelope (7). After that the capsid enters the cytosol, decays, and releases genome (7). After the virus enters the host cell the virus begins making copies of itself inside the rough endoplasmic reticulum (7).
Currently Brazil is going through an ongoing outbreak of yellow fever. The first cases were spotted in December 2016 in Minas Gerais (2). Since then there have been reported cases in the surrounding areas such as Espirito Santo, Sao Paulo, and Rio de Janeiro (2). Since March 16, 2017, the yellow fever has been spreading to the Atlantic coast of Brazil in places that were not thought to be at risk for yellow fever (3). They updated the travel notice to level 2 which means you should practice enhanced precautions when visiting Brazil (2). It is recommended that anyone older than 9 months old should get vaccinated and those without the vaccination should stay away from these areas (2). If you are traveling to one of these areas, it is recommended that you get a vaccine or booster 10 days before your trip (2). It is also recommended that you prevent mosquito bites using long sleeved clothes, bug spray with DEET, sleep in screen or air conditioned rooms, and use a bed net (2).
The International Coordinating Group on Vaccine Provision has approved the release of over 3.5 million doses of vaccine (4). The yellow fever vaccine provides up to 99% immunity but the vaccines take a long time to produce and they don’t have many of them in storage (5). Currently the country is already one of the top yellow fever vaccine manufacturers in the world (4). Normally Brazil would be able to take care of its own vaccinations but there has been a big increase in the number of people found with yellow fever (4). More than 30 million people were vaccinated in the emergency vaccination campaigns in Angola and the Democratic republic of Congo in 2016 (5). As the vaccines ran low they had to decrease the dosage to a fifth of its original amount so they could get it to more people (5). Brazil has distributed 12.5 million doses of the vaccine but it is hard to get it to everyone because some people live in dispersed remote areas away from the general population (5). They are also controlling the population of mosquitos there to prevent the spread through vector transmission (5).
Since March 13 there has been 1,538 reported cases and 255 deaths from yellow fever (4). So far the World Health Organization said that there is no evidence saying that the Aedes Mosquitos are spreading the virus (4). The current outbreak is reported to be spread by the Haemagogus and Sabethes mosquitos (5). The fatality rate for the outbreak of yellow fever is 33% for confirmed cases and 11% for suspected cases (5).
This disease has the potential to cause serious problems to a country especially if it gets into the Aedes mosquito and can spread from human to human rapidly. With the virus using the Aedes mosquito as a vector it has the potential to spread through Americas east coast rapidly if someone somehow gets infected and get bitten by the mosquito. Fortunately though we have a yellow fever vaccine to combat the disease and prevent the excessive spread of the disease. The issue right now in Brazil is being able to get the vaccine to everyone because of how spread out people are throughout the country. Ways to avoid being infected are mostly vector control and avoidance because other than mosquitos it is hard to get this disease. Once again mosquitos cause the spread of another disease so the best way of eradicating this disease as well as many other diseases in my opinion would be wiping out the mosquito population. The main issue I can think of with eradicating mosquitoes is the impact it would have on any animals that feed on them.
Citations
- https://www.cdc.gov/yellowfever/
- https://wwwnc.cdc.gov/travel/notices/alert/yellow-fever-brazil
- http://www.who.int/csr/don/20-march-2017-yellow-fever-brazil/en/
- https://www.statnews.com/2017/03/21/brazil-yellow-fever-vaccine/
- http://www.cnn.com/2017/03/09/health/yellow-fever-outbreak-brazil/
- http://www.medicinenet.com/yellow_fever/page4.htm