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Yellow Fever Outbreaks

Yellow Fever Outbreaks July 2025

Scientists believe yellow fever has existed for about 3,000 years, originating in Africa and spreading to the Americas in the 17th century. In the 18th and 19th centuries, yellow fever (YF) was considered one of the most dangerous mosquito-transmitted infectious diseases. According to the World Health Organization (WHO), as of July 2025, the YF virus has become endemic in tropical areas of Africa and 13 countries in the Americas. As of June 29, 2025, the overall risk associated with the yellow fever virus in the Americas Region, particularly in endemic countries such as Brazil, is classified as ¨High.¨

Africa Yellow Fever Outbreak

Since the beginning of 2023, documented probable and confirmed cases of yellow fever have been reported in Burkina Faso, Cameroon, the Central African Republic, Chad, the Republic of the Congo, Côte d'Ivoire, the Democratic Republic of the Congo, Guinea, Niger, Nigeria, South Sudan, Togo and Uganda. In July 2025, the Angolan Ministry of Health reported seven confirmed cases of yellow fever from 5 provinces: Luanda, Benguela, Malanje, Huíla, and Huambo. On March 28, 2024, the U.S. Centers for Disease Control and Prevention (CDC) issued a Level 2 Travel Health Notice regarding a yellow fever outbreak in Nigeria. Between January 2024 and November 2024, 29 confirmed YF cases were reported in Nigeria. The overall risk at the regional level was reassessed as moderate.

The Americas' Yellow Fever Outbreaks

Yellow fever human cases and deaths by country and sub-national geographic distribution from 2000 to 2022 are posted by the PAHO. As of June 2025, countries in the Americas Region had reported about 200 confirmed human cases of yellow fever, including 85 deaths (CFR 40%). Yellow fever cases were reported in the Plurinational States of Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, and the Bolivarian Republic of Venezuela. In 2024, 61 human cases of yellow fever were confirmed in the Americas Region, including 30 deaths (CFR= 50%), among five countries: Bolivia, Brazil, Colombia, Guyana, and Peru. In February 2025, the PAHO published a Public Health Risk Assessment related to yellow fever, confirming the high risk of YF outbreaks in the Americas. On April 15, 2025, the U.S. CDC issued a Level 2 - Practice Enhanced Precautions, Travel Helath Advisory regarding YF outbreaks in the Americas. In 2024, the PAHO reported 61 YF cases, 30 of which were fatal.

In Brazil, yellow fever transmission historically occurs within a sylvatic cycle in the Amazonian Region. Between 2020 and 2025, three cases of yellow fever were confirmed in the Peixe and São Salvador regions. São Paulo State Health Department confirmed that 679 human cases were recorded from 2000 to 2023. Brazil experienced its largest recorded outbreak of yellow fever in 2018. Yellow Fever cases have been confirmed in Pará State, Amazon Region of Brazil, for three decades. In March 2025, five confirmed deaths and 27 cases of YF were reported on Marajó Island. As of 2025, Australia, the U.S. CDC, Hong Kong, and the United Kingdom have issued travel alerts regarding Brazil's YF outbreaks.

Bolivia reported three YF cases, including one death (CFR 33%), in the city of Palos Blancos in the La Paz Department in 2025. Eight YF cases occurred in 2024 and five in 2023.

Since October 2024, the YF virus has appeared in areas not previously affected in past years in the Colombian department of Tolima. As of June 9, 2025, there have been 104 cases, with 45 deaths, primarily in Tolima. Although the vaccine for yellow fever was incorporated into Colombia's national immunisation schedule for children in 2002 in endemic regions, coverage remains low among adults.

The Ecuadorian Ministry of Public Health reported 10 confirmed fatal yellow fever cases and eight related fatalities as of June 21, 2025, from the provinces of Morona Santiago and Zamora Chinchipe.

Peruvian authorities issued an epidemiological alert due to a sharp rise in yellow fever cases in areas of the Peruvian Amazon in 2025, including Huánuco, San Martín, and Amazona districts. As of April 24, 2025, Peru has reported 32 confirmed cases of yellow fever, resulting in 10 deaths. In comparison, Peru reported 19 confirmed cases of yellow fever, with nine deaths, for 2024.

United States Yellow Fever Outbreaks

In the United States, the Butte County Mosquito and Vector Control District in California detected the Aedes aegypti (yellow fever) mosquito in 2023. Aedes aegypti mosquitoes were found for the fourth consecutive year in Butte County. The American Society for Microbiology provides a history of the emergence of yellow fever outbreaks in the United States.

Yellow Fever Vaccine Availability 2025

Various yellow fever vaccines are authorized and commercially available in the U.S. as of 2025.

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Reviewer:

Robert Carlson, MD

Last Reviewed:

Tuesday, July 8, 2025 - 17:40

Description:

Yellow fever outbreaks in Africa, the Americas, and Oceania reported in 2025.

Vaccine:

YF-VAX Yellow Fever Vaccine

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According to the U.S. Centers for Disease Control and Prevention (CDC), measles cases increased by about 80% in 2022 compared to the previous year.

In addition, travel experts continue to warn of expanding measles outbreaks in 2023.

For example, the CDC's top ten list of measles outbreaks is led by India, which has reported over 47,979 cases over the past year.

To emphasize this health risk, the CDC issued a Global Measles Watch - Level 1, Practice Usual Precautions notice on April 6, 2023.

While the U.S. has reported very few measles cases this year, recent cases in Kentucky, Utah, and Ohio have been highlighted in national media.

As of March 30, 2023, the CDC reported six measles cases in 2023 and 121 cases in six U.S. jurisdictions during 2022.

To reduce traveler's health risk, measles is a vaccine-preventable disease, with various vaccines approved in the U.S. and available to local clinics and community pharmacies.

Vaccine Treats:

Measles

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CDC measles outbreaks April 6, 2023

Live Blog Update Author:

Don Hackett

Location Tags:

Worldwide

Vaccine:

Priorix Vaccine

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The U.S. Centers for Disease Control and Prevention (CDC) recently reissued a Watch - Level 1, Practice Usual Precautions notice regarding the Republic of Paraguay's chikungunya virus outbreak.

On April 6, 2022, the CDC confirmed that Paraguary's departments had reported chikungunya cases in 2023.

Furthermore, recent chikungunya cases have been reported among US travelers returning from Paraguay.

Since no approved vaccines target chikungunya, the CDC says people can protect themselves by preventing mosquito bites.

Furthermore, the CDC says travelers should seek medical care if they develop fever, joint pain, headache, muscle pain, joint swelling, or rash.

Additional chikungunya outbreak news is posted at Vax-Before-Travel.

Vaccine Treats:

Chikungunya

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U.S. CDC Watch - Level 1, Practice Usual Precautions - Paraguay

Live Blog Update Author:

Don Hackett

Location Tags:

Asunción

Vaccine:

Chikungunya Vaccine (VLA1553)

More Mpox Vaccine Breakthrough Cases Confirmed

Jynneos vaccinations recommended pre and post Mpox infection

April 9, 2023

Fact checked by Robert Carlson, MD

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The Swiss Public Health Agency recently announced no COVID-19 vaccination is recommended for spring/summer 2023. However, people at especially high risk can receive a vaccination after consultation with their doctor.

As of April 8, 2023, the Federal Office of Public Health stated nearly everyone in Switzerland had been vaccinated and/or contracted and recovered from COVID-19.

Therefore, almost everyone's immune system has been exposed to the SARS-CoV-2 coronavirus.

And in the spring/summer of 2023, the virus will likely circulate less, and the current variants also cause mild illness.

For autumn 2023, the vaccination recommendation will be re-evaluated and adjusted accordingly.

Vaccine Treats:

COVID-19

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Gordon Johnson

Live Blog Update Author:

Don Hackett

Location Tags:

Bern

Vaccine:

Novavax COVID-19 Vaccine

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The World Health Organization (WHO) published a Weekly Epidemiological Update Edition #137 regarding the COVID-19 pandemic on April 5, 2023.

The WHO disclosed a decrease of 28% in new COVID-19 cases and 30% in related fatalities, respectively, compared to the previous 28 days (February 6 to March 5, 2023).

Despite this overall downward trend, it is essential to note that 74 (31%) countries have reported increases in new cases of 20% or greater during the last 28 days compared to the previous 28-day period.

As of April 2, 2023, over 762 million confirmed cases and over 6.8 million deaths have been reported globally.

Furthermore, the WHO continues Listing numerous COVID-19 vaccines available in various countries.

Vaccine Treats:

COVID-19

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WHO data April 7, 2023 - COVID-19 pandemic

Live Blog Update Author:

Karen McClorey Hackett

Location Tags:

Geneva

Vaccine:

Novavax COVID-19 Vaccine

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BioSpace reported today Vivek Shinde, vice president of clinical development and lead for older adult influenza & RSV vaccines at Novavax Inc., delivered an update on the Company's COVID-influenza combination (CIC) candidate at the World Vaccine Congress 2023.

The Company presented CIC data and poster presentations on its COVID-19 prototype vaccine during this conference in Washington, DC.

Shinde confirmed that CIC formulations were immunogenic and induced strong functional antibody and CD4+ T cell responses against SARS-CoV-2 and multiple influenza strains on April 5, 2023.

"I think a combination vaccine is only going to hopefully boost compliance in those who intend to get both vaccines," he informed Heather McKenzie at BioSpace on April 7, 2023.

Novavax intends to use these data to inform an ongoing Phase II dose confirmation study. Results from this study are expected later in 2023.

Novavax's COVID-19 vaccine (Nuvaxovid™, CovoVax™, NVX-CoV2373) protein-based vaccine has received various authorizations from more than 43 countries.

Vaccine Treats:

Influenza

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from Pixabay

Live Blog Update Author:

Don Hackett

Location Tags:

Washington DC

Vaccine:

Novavax COVID-19 Vaccine

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Researchers at the Oak Crest Institute of Science have been exploring new ways to prevent the spread of HIV-1 among young women in low and middle-income countries.

Some questions have been answered in a new study, and the answers may be surprising.

In a recent study published by the journal Nature on March 21, 2023, using humanized mice (mice that have received implants of human cells and tissues so that they can be infected with HIV-1), researchers tested the vaginal HIV-1 prevention efficacy of single and combination antiviral compounds applied locally.

They used a mathematical model to empirically study the effects of administering different doses of antiviral drugs.

The results were unexpected: when tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) – both drugs that share the same mechanism of inhibiting HIV-1 reverse transcriptase, thereby preventing viral replication in immune cells – were combined with a third drug that used a different mode of action against HIV-1, a strong antagonistic effect was observed.

This means that the drugs were less effective when used together than they were when used separately.

'Our approach provides a translational template for the preclinical, rational, and systematic evaluation of drug combinations for the prevention of HIV-1 and other viral diseases,' wrote these researchers.

As of April 7, 2023, there are no approved HIV vaccines available.

Vaccine Treats:

HIV

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by Gerd Altmann

Live Blog Update Author:

Karen McClorey Hackett

Location Tags:

California

Vaccine:

Apretude HIV PrEP

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The Wyoming State Veterinary Laboratory (WSVL) recently diagnosed the highly pathogenic avian influenza (HPAI) virus in a barn cat near Thermopolis, WY. This is the first report of HPAI in a domestic cat in Wyoming, and it likely became infected from ingesting meat from wild waterfowl.

'We know that wild birds, particularly waterfowl, have been affected in large numbers by HPAI, but in recent months we have detected the virus in wild carnivorous mammals, including mountain lions and a red fox,' wrote WSVL in April 2023.

As the HPAI outbreak continues, please ensure you use gloves and masks when handling sick or dead mammals and birds. And report any sick wildlife through the Wyoming Game and Fish Department's Wildlife Health Laboratory online reporting tool at this link.

Additionally, various mammals infected with bird flu have been reported in Canada, Mexico, and South America in 2023.

And about eleven humans have recently been infected with this version of bird flu.

As of April 7, 2023, there are U.S. Food and Drug Administration-approved avian influenza vaccines, with several vaccine candidates conducting studies. Furthermore, annual flu shots are not effective against bird flu viruses.

Vaccine Treats:

Bird Flu

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by Andreas Lischka

Live Blog Update Author:

Karen McClorey Hackett

Location Tags:

Laramie

Vaccine:

Audenz Influenza A(H5N1) Vaccine

0 min read

The Centers for Disease Control and Prevention (CDC) recently issued Health Alert Network Health Advisory CDCHAN-00489, informing clinicians and public health departments about Marburg virus disease (MVD) outbreaks in Equatorial Guinea and one in Tanzania.

As of April 7, 2023, there is no evidence to suggest that these outbreaks are related, as most experts agree that these represent two independent animal-to-human spillover events.

To date, no confirmed cases of MVD related to these outbreaks have been reported in the U.S. or other countries outside Equatorial Guinea and Tanzania.

This CDC Health Advisory aims to increase awareness of the risk of imported cases in the U.S.

It also summarizes CDC’s recommendations for case identification, testing, and clinical laboratory biosafety considerations in the U.S.

Furthermore, the CDC confirmed no vaccines or treatments are authorized specifically for MVD.

Vaccine Treats:

Marburg Virus

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