Did you know that there are currently 34 countries in Africa and 13 countries in the Americas with this virus?

The spread of viral diseases through emerging and re-emerging vectors represents a significant concern for global health. Yellow fever is an endemic infectious disease characterized mainly by symptoms such as constant fever, decay, muscle pain, relative bradycardia and bilious or hemorrhagic vomiting, transmitted mainly by Aedes and Haemogogus mosquitoes, which are found mainly in warm and tropical areas. Its high mortality has led it to be considered a constant threat to public health (Alcalá & Dávila; 2024).

This virus is characterized by an incubation period of 3 to 6 days, its infectious phase is characterized by chills, fever, myalgia, headache, muscle pain, mild epistaxis, albuminuria and jaundice, this symptomatic phase can last up to 8 days. After the infectious phase, approximately 10% have a process of intoxication, where the virus stops circulating through the bloodstream and takes root in internal organs such as the liver, spleen and heart, generating hemorrhagic complications.

The virus is transmitted mainly by previously infected effective vectors that allow direct virus spread, such as Aedes mosquitoes whose ability to reproduce in tropical urban areas contributes significantly to the transmission of this virus.

At the moment there is no specific treatment for this virus, so only symptom management is performed, which is why its prevention and early detection is important to avoid mortality due to mismanagement.

On February 4, the Pan American Health Organization issued an epidemiological alert due to the considerable increase in the number of cases reported in countries such as Colombia, Peru, Ecuador and Brazil, with seven deaths and 19 cases reported this year and 61 reported last year. The high number of reported cases generates the need to intensify efforts to prevent and diagnose the virus in time, this will improve the epidemiological surveillance of different health entities.

Its diagnosis is mainly based on the detection of the virus by polymerase chain reaction with reverse transcription in early stages or serological tests of IgG and IgM (elisa tests) in more advanced stages of infection. One of the main diagnostic problems is the cross-reaction that ELISA tests can generate in patients with a history of other infections caused by flaviviruses such as dengue, generating false positives, so greater accuracy is recommended with the detection of viral RNA, which is characterized by a genome composed of positive-sense single-stranded RNA. Currently there is only one serotype with 5 different genotypes in the areas where the virus is present.

Although yellow fever continues to be a public health challenge due to its resurgence not only in Latin America, but also again in Africa, it has a highly effective preventive vaccine based on an attenuated viral load, which allows the immune system to generate antibodies 5 days after administration of the vaccine, reaching maximum levels of protection 10 days after its application. The Pan American Health Organization reports that the cases reported between 2024-2025 corresponded to people who had not received the vaccine, and urges countries to continue strengthening their vaccination programs, as well as to take appropriate measures to inform and protect travelers going to risk areas.

No one is immune to yellow fever and it occurs in people of all ages and races. The highest mortality rates are recorded in infants and the elderly, who often have depressed immune systems, which is why it is important to be attentive to its symptoms, diagnosis and prevention, this will allow strengthening epidemiological surveillance programs through detailed monitoring of the distribution and activity of vectors, with a special focus on regions with greater propensity to outbreaks and spread of diseases transmitted by different vectors.

 

See the latest PAHO report on yellow fever in the Americas: Click here

 

Bibliography

• ALCALA FERRAEZ, Carlos and DAVILA VALDES, Claudia. Yellow fever and immunity between 1906 and 1919: susceptible persons. Peninsula [online]. 2024, vol.19, n.2 [cited 2025-02-09], pp.9-33.
• Alvarez, Y. S., Rodríguez, E. C., del Pilar Toledo, G., & Rodríguez, D. YELLOW FEVER REAPPEARS, FORGOTTEN BY ALL.
• Matos, H. J. (2023). Climate transition, arbovirus explosion and the specter of Yellow Fever. An epidemiological view.
• Yglesias-Rosales, M., Rodríguez-González, A., & Rojas-Montero, M. (2005).
• Yellow fever: a latent danger. Acta Médica Costarricense, 47(3), 118-125.
• Weitzel, T., Perret, C., Valdivieso, F., Abarca, K., & Vial, P. (2018). Yellow fever vaccination for Chilean travelers to Brazil. Practical considerations. Revista chilena de infectología, 35(5), 587-590.