Infectious Diseases A to Z – Yellow Fever

With this new column, Elite Healthcare will compile an index of various infectious diseases, with occasional highlights of emerging conditions. 

Yellow Fever

General definition and information:

An extremely rare virus in the United States, as well as U.S. residents who travel abroad, yellow fever is a chronic condition spread through bites from infected mosquitoes that has no cure or medication for treatment, although vaccination is available. The vaccine has been available for more than 80 years, and so most Americans have been protected from the virus for some time, but the World Health Organization still considers it to be a current threat and the potential for outbreaks is said to exist globally even in locations that have never had documented cases reported because the appropriate mosquito vector remains present in these areas. In the U.S., the Aedes aegypti mosquito, aka “the yellow fever mosquito,” an insect that can transmit the virus, as well as the Zika virus and other serious diseases, were reportedly discovered as recently as this summer in the eastern part of Stanislaus County in Modesto, CA.(1) This marks the first time that the mosquito has been reported in Stanislaus County, and local healthcare officials are expressing concerns even though there have been no local cases of transmission reported.

Modes of Transmission:

Transmitted primarily through the bite of infected mosquitoes (the Aedes or Haemagogus species) that contract the virus after feeding on infected primates, yellow fever has three transmission cycles, according to the Centers for Disease Control and Prevention (CDC):(2) the sylvatic, or “jungle,” cycle; the intermediate, or “savannah,” cycle; and the “urban” cycle, which is typically brought to an urban setting by a human who becomes infected by the virus after traveling to the jungle or savannah. The jungle cycle involves the transmission of the virus between non-human primates and mosquitoes found in the forest canopy. Humans are ten infected when visiting or working in the jungle. The savannah cycle involves the transmission of the 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, according to the CDC.

Initial symptoms include initial sudden fever onset with chills, severe headache, back pain, and general body aches, nausea and vomiting, and fatigue and general malaise, although most people will not display symptoms. Most people who experience the initial symptoms are expected to improve within one week, however, for some patients, the weakness and fatigue could last several months even though they’ve primarily “recovered.” Others may develop a more severe form of the disease while some patients will experience a brief remission lasting hours or for one day, only to then develop by a more severe form of the disease that is marked by high fever, jaundice, bleeding, shock, and potentially organ failure. According to the CDC, 30-60% of patients who develop a severe form of the disease die.(3) Diagnosis is typically confirmed based on laboratory testing compared with the patient’s travel history.

Treatment Strategies:

There is no acceptable suggested treatment for yellow fever, according to CDC officials. In fact, certain medications, such as aspirin and other nonsteroidal anti-inflammatory drugs including ibuprofen and naproxen, should be avoided due to an increased risk of bleeding. Those patients who develop severe symptoms should be hospitalized for close observation and supportive care. Rest, increased fluid intake, and the use of other pain relievers and medication that reduce fever and relieve aching may also be prescribed to the at-home patient. Any patients who are seen in the healthcare setting who have recently returned from travel and have any symptoms related to the virus should be considered at risk of having yellow fever. 

Prevention Parameters:

The remains the most effective measure that anyone can take and is available as a single dose that provides protection for most people for their entire life. The CDC recommends the vaccine for all people aged 9 months or older, as well as those who are traveling to or living in areas at risk for the yellow fever virus in Africa and South America.(4) The vaccine may actually be required for entry into certain countries as a preventive measure. The CDC offers a resource that explains certain vaccination requirements and recommendations for specific countries around the globe.(5)

CDC officials do warn that the vaccine poses a “theoretical risk” to pregnant women and their unborn children because the vaccine contains live virus vaccine, even though the vaccine has been administered to many pregnant women without any apparent adverse effects on the fetus. Still, the CDC suggests that pregnant women avoid or postpone travel to an area where there is a risk of yellow fever. Patients who do travel and do display symptoms of yellow fever should be encouraged to protect themselves from mosquito bites for up to five days after symptoms begin to help prevent the spreading of the virus to uninfected mosquitoes that can then spread the virus to other people. Any healthcare providers who learn of patients or members of their community who are planning to travel to Brazil should inform them of a large, ongoing outbreak currently being monitored.(6) CDC officials also offer a website that displays warnings to healthcare providers and the general public about travel notices that may be important to consider.(7)


  1. Demsky M. Mosquitoes Capable of Transmitting Zika and Yellow Fever Viruses Found in Stanislaus County. Fox News. 2019. Accessed online:
  2. Yellow Fever Symptoms, Diagnosis, & Treatment. CDC. 2019. Accessed online:
  3. Yellow Fever Vaccine. CDC. 2019. Accessed online:
  4. Travelers’ Health Destinations. CDC. 2019. Accessed online:
  5. Yellow Fever in Brazil. CDC. 2018. Accessed online:
  6. Travelers’ Health – Vaccines, Medicines, & Advice. CDC. 2019. Accessed online:

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