Vaccine News

The chikungunya epidemic in Bolivia's Santa Cruz department appears to be easing slightly. The Departmental Health Service (SEDES) has reported a noticeable decline in new cases of this mosquito-transmitted virus.

According to SEDES epidemiologist Carlos Hurtado, the latest epidemiological week recorded 655 positive chikungunya cases, a decrease of approximately 300 cases compared to the previous week.

This brings the cumulative total for 2026 in Santa Cruz, the primary epicenter of the outbreak in Bolivia, to 4,283 positive cases.

Despite this decline, the positivity rate remains high at 51%, indicating that more than half of those tested are infected with the East/Central/South African genotype of the chikungunya virus.

The U.S. Centers for Disease Control and Prevention (CDC) has issued a Level 2 Travel Health Notice for Santa Cruz and Cochabamba due to the outbreak. They advise travelers to use insect repellents, wear protective clothing, and consider vaccination where appropriate.

Bolivia is not alone in reporting chikungunya cases this year.

Recent data indicate that over 29,000 cases and 85 chikungunya-related fatalities have been reported by early March.

As of March 9, 2026, the main available vaccine option in the United States and select countries is VIMKUNYA®, a non-live virus-like particle vaccine produced by Bavarian Nordic A/S.

This travel vaccine was approved by the U.S. FDA in 2025 and is commercially available at travel clinics and pharmacies.

Recent detections of poliovirus in London's wastewater have led the U.S. Centers for Disease Control and Prevention (CDC) to update its global travel health notice to include the United Kingdom.

This CDC advisory, classified as Level 2 – Practice Enhanced Precautions, was issued on March 3, 2026, and highlights the ongoing risk of poliovirus circulation in over 30 countries, where environmental surveillance has found traces of the virus in sewage samples.

In the UK, detections have primarily been concentrated around the Beckton Sewage Treatment Works, which serves millions of residents in northern and eastern London. According to the UK Health Security Agency (UKHSA), a circulating vaccine-derived poliovirus type 2 (cVDPV2) was identified in an environmental sample collected around January 28, 2026.

Investigations into the source of the cVDPV2 detections in London are ongoing and may be linked to international arrivals.

This indicates a continued presence of poliovirus in the UK's wastewater system, following earlier discoveries in late 2024 in locations such as East Worthing, Leeds, and London's Beckton and Crossness treatment plants.

Notably, similar UKHSA detections in London's sewage began in 2022.

While no cases of paralytic polio have been reported in the UK since 1984, these environmental detections suggest potential silent transmission in communities with low vaccination rates. Health officials emphasize the importance of maintaining high vaccination coverage to prevent any resurgence of the virus.

Vaccine-derived poliovirus occurs when the weakened live virus used in oral polio vaccines (OPV) mutates and regains the ability to spread in under-immunized populations. Although the UK switched to the inactivated polio vaccine (IPV) in 2004, which does not carry this risk, global travel and migration can introduce strains from regions where OPV is still used.

The updated CDC advisory includes endemic hotspots like Afghanistan, Pakistan, and Nigeria, as well as non-endemic countries such as the UK, Germany, Finland, and Spain, where wastewater detections have been reported. CDC experts highlight that wastewater surveillance acts as an early warning system, enabling public health officials to intervene before outbreaks occur.

The notice states, "Some international destinations have circulating poliovirus," urging travelers to ensure they are up to date on their polio vaccines before any international trip.

The CDC advises clinicians to prioritize completing the IPV series for individuals who are unvaccinated or incompletely vaccinated and planning to travel. They emphasize that polio can lead to lifelong paralysis or death in rare cases.

The CDC also recommends a single lifetime IPV booster dose for adults who have completed the full routine polio vaccine series before visiting affected areas.

In numerious countries, the novel OPV (nOPV2) vaccine has been administered over 2 billion times in the past few years.

With global efforts intensifying, there is hope that these early alerts will keep the UK and other nations one step ahead of the virus, according to the CDC.

The U.S. Department of State has issued an important reminder for Americans planning spring break trips to Mexico. Travelers are urged to remain aware of ongoing safety risks, even though recent widespread violence has lessened.

In a Message to U.S. Citizens released on March 2, 2026, the U.S. Embassy in Mexico emphasizes the importance of personal responsibility with the slogan: "Travel Smart – Be Informed." 

The State Department advisory states that while large-scale unrest, triggered by Mexican security operations on February 22, 2026, has subsided, risks such as crime and kidnapping persist. 

As spring break 2026 attracts large crowds to Mexico's beaches and resorts, officials stress the importance of reviewing the full advisory and the country information page at travel.state.gov. Travelers are encouraged to stay informed by closely monitoring updates, as security situations can change quickly.

Mexico currently holds an overall Level 2 advisory: Exercise Increased Caution. However, conditions vary greatly by region, with six states classified as Level 4: Do Not Travel in 2026.

Furthermore, the U.S. CDC has identified a significant number of health risks in Mexico.

For emergencies when visiting Mexico, contact the U.S. Department of State's Consular Affairs line at +1-888-407-4747 or +1-202-501-4444.

The Ministry of Health, Wellness, and Nutrition in Saint Lucia recently confirmed a laboratory-positive case of the Chikungunya, marking the first such case on the island since 2021. The patient ully recovered and been discharged.

As of March 6, 2026, local health authorities report no additional cases.

However, enhanced surveillance, contact tracing, and intensified mosquito control efforts are underway to prevent any potential spread. Aedes mosquitoes primarily spread Chikungunya, the same vectors that carry dengue and Zika. 

Despite this single case, tourism in Saint Lucia remains robust. the Saint Lucia Tourism Authority reported a record-breaking January 2026, which welcomed 37,691 stay-over arrivals. Saint Lucia continues to attract vacationers seeking its beaches, Pitons, luxury resorts, and eco-adventures. 

This growth was primarily driven by an 11% increase in visitors from the United States.

This isolated case comes amid broader regional increases in chikungunya virus activity across parts of the Caribbean and Americas, as noted in alerts from the Pan American Health Organization (PAHO).

The isolated chikungunya case has not triggered widespread PAHO advisories or reduced traveler activity in the Americas in 2026.

Vaccine and prevention recommendations remain important for both travelers and residents.

The chikungunya vaccine (VIMKUNYA) is approved in the United States for individuals aged 12 and older and is recommended for travelers to areas with ongoing chikungunya outbreaks or transmission.

Spanish health authorities have informed the European Centre for Disease Prevention and Control (ECDC) of a confirmed case of human infection with the swine influenza A(H1N1)v virus. 

This case was identified in February 2026 in the autonomous region of Catalonia. The patient remained completely asymptomatic, showing no flu-like symptoms such as fever, cough, or malaise, and has since made a full recovery. 

Notably, the individual had no known history of exposure to pigs, pig farms, or contaminated environments, which distinguishes this case from most previous zoonotic infections. As of March 3, 2026, all identified close contacts tested negative, and there was no evidence of secondary transmission.

This marks the fourth human case of swine influenza A(H1N1)v reported in Spain over the past 17 years. Fortunately, there has never been documented human-to-human transmission of the A(H1N1) virus in Spain.

Catalonia, located in the northeast, is one of Spain's most intensive pig-rearing regions and has recently faced separate challenges due to detections of African swine fever in wild boars in the Barcelona area. 

The ECDC's Communicable Disease Threats Report (Week 9, 2026) states, "Based on the information currently available, the likelihood of further transmission of variant A(H1N1) linked to this event is assessed to be very low."

According to the latest available data from the U.S. CDC, there have been no confirmed cases of variant swine-origin influenza (A(H1N1)v, A(H1N2)v, or A(H3N2)v) reported for the ongoing 2025–26 flu season.

However, during the 2024–2025 flu season, one confirmed human case of swine-origin variant A(H1N2)v infection was reported in Iowa. The adult patient was hospitalized but made a full recovery.

According to the U.S. CDC, seasonal influenza vaccines for 2026 provide no direct protection against swine-origin variant virus strains seen in recent European cases, as those belong to different genetic lineages.

A major study recently published in The Journal of Infectious Diseases details a significant measles transmission event linked to an unvaccinated adult who traveled from Europe to Colorado while infectious with the virus.

This article emphasizes the risks associated with air travel in spreading this highly contagious disease and underscores the essential role of vaccination.

The incident is described as one of the most extensive air travel-related measles transmission chains documented in the United States in recent years, with the virus spreading across flights, airport areas, and beyond.

However, as of March 3, 2026, there is no mandatory measles vaccination policy in the U.S. for domestic or international air travel when a person is departing from a measles outbreak area.

Investigators identified 135 travelers who were exposed through aircraft contact tracing. Ultimately, 15 secondary cases arose among those exposed: 5 during the international flight, 3 on the domestic flight, and 7 at the airport transit area. Additionally, 2 tertiary cases were linked to further community spread.

Notably, 5 of the secondary cases had documentation of at least one prior measles vaccination, indicating that breakthrough infections can occur.

The study's authors conclude that measles transmission can easily occur during travel in enclosed environments such as aircraft cabins, where the virus can remain airborne for up to two hours.

Most health agencies strongly recommend that all travelers aged 6 months and older receive measles vaccinations before international travel.

This outbreak highlights broader concerns about rising measles cases in the U.S. and globally, largely driven by gaps in vaccination coverage.

Public health experts worldwide continue to advocate for routine measles immunization as the most effective prevention strategy against such outbreaks.

On March 2, 2026, the U.S. Centers for Disease Control and Prevention acting director and head of the NIH, Jay Bhattacharya, MD, PhD, posted a video on X promoting the measles vaccine.

"Measles is preventable, and vaccination remains the most effective way to protect yourself and those around you," Dr. Bhattacharya stated.  

Venezuelan health authorities are addressing a significant resurgence of yellow fever (YF), with 36 laboratory-confirmed human cases since the outbreak began in mid-2025.

As of late February 2026, these mosquito-transmitted cases have been reported across 14 states, indicating a wide geographic spread that surpasses the more localized patterns seen in previous outbreaks.

So far, the disease has remained limited to forest exposures, with no evidence of urban transmission by Aedes aegypti mosquitoes.

Recent public reports have not detailed any related fatalities, though severe YF cases typically have a case-fatality rate of 20–50%.

Venezuela's YF outbreak occurs amid increased activity across the Americas. 

In 2024, the region reported 61 confirmed human cases and 30 deaths. By mid-2025, this number surged threefold to over 200 confirmed cases and 85 deaths (with a case-fatality rate of approximately 40%) across several countries, including Brazil, Colombia, Peru, Bolivia, and Ecuador, according to data from the Pan American Health Organization (PAHO).

Subsequent PAHO updates reported even higher totals, with YF outbreaks expanding beyond traditional Amazonian zones into new areas, including Colombia's Tolima department in 2026.

This resurgence serves as a stark reminder of yellow fever's capacity to exploit vaccination gaps in endemic settings.

According to the PAHO, the minimal childhood vaccination coverage—below 80% in Venezuela and several other endemic countries—coupled with climatic factors that favor mosquitoes, has contributed to the intensification of YF outbreaks.

PAHO has repeatedly assessed the risk of yellow fever outbreaks in the Americas as high and has issued multiple epidemiological alerts in 2025, urging mass vaccination in at-risk areas. In response to the current outbreak in Venezuela, emergency vaccination campaigns have been launched, targeting high-priority parishes, particularly in rural and border areas.

The single-dose Stamaril (YF-VAX) vaccine provides lifelong immunity. While proof of yellow fever vaccination is not required for direct arrivals to Venezuela from non-endemic countries like the United States, it is mandatory for travelers aged 1 year and older arriving from or transiting through countries with a risk of transmission, such as Brazil and Colombia.

As of March 2, 2026, the U.S. Centers for Disease Control and Prevention strongly recommends vaccination for most travelers visiting areas below approximately 2,300 meters in elevation, including popular sites like Angel Falls. In the U.S., the YF-VAX vaccine is commercially offered at travel clinics.

However, it is generally not recommended to vaccinate for travel limited to major cities such as Caracas or Valencia.

Separately, the U.S. Department of State maintains a Level 4: Do Not Travel advisory for Venezuela, citing severe risks to visitors in March 2026.