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The Chicago Department of Public Health (CDPH) recently confirmed the first three human cases of West Nile virus (WNV) this year. The Illinois Department of Public Health previously confirmed the first human case of WNV in the state on June 24, 2025.
The patients, whose symptoms began in late July or early August, reside on the Northwest and South sides.
WNV is the most common cause of mosquito-borne disease in Chicago.
CDPH has a robust mosquito control program, which includes treating over 80,000 catch basins in Chicago with larvicide to kill immature mosquitoes, collecting and testing mosquitoes for WNV, and spraying in specific geographic areas to kill adult mosquitoes if needed.
Licensed mosquito abatement technicians are dispensing an ultra-low-volume spray from trucks.
CDPH has sprayed insecticide in nine different community areas over the last several weeks and will be spraying to kill adult mosquitoes in seven communities in mid-August 2025 (Forest Glen, Norwood Park, Mount Greenwood, Beverly, East Garfield Park, Near West Side, and North Lawndale).
"We are seeing a higher proportion of mosquitoes testing positive for West Nile virus than usual this year," said CDPH Commissioner Olusimbo 'Simbo' Ige, MD, MPH, in a press release on August 12, 2025.
"The best way to protect yourself from West Nile virus is to avoid mosquito bites and take measures to stop them from breeding around your home."
CDPH says WNV is typically spread to humans via the bite of an infected mosquito and is not generally spread from person to person. While most people infected with WNV do not feel sick, about 1 in 5 people develop a fever and flu-like symptoms.
Severe illness can occur in about 1 in 150 people and is most likely in people over age 60. Because there are no specific medications to treat WNV in people, the most effective method to prevent infection is to avoid mosquito bites.
In Europe, six countries have recently reported WNV cases.
As of August 14, 2025, there are no approved WNV vaccines available in the United States.
In Denmark, vaccination has nearly eliminated infections caused by high-risk strains of Human Papillomavirus (HPV) 16 and 18 among women who were vaccinated as adolescents.
The prevalence of HPV16/18 types was low and stayed stable over time, at 1% 95% CI: 0.8–1.2) in the first samples, 0.6% (95% CI: 0.4–0.9) in the second, and 0.6% (95% CI: 0.3–1.0) in the third samples.
Before vaccination, the prevalence of HPV16/18 was between 15% and 17%.
A study published in Eurosurveillance in July 2025 highlights this finding as significant, given that these HPV types are responsible for over 70% of cervical cancer cases.
These researchers wrote, 'To our knowledge, this is the first study to report on HPV status in consecutive rounds of cervical cell sampling in a cohort of young women offered 4-valent HPV vaccination as girls.'
In 2008, Denmark started to offer free vaccination against HPV with the 4-valent vaccine to teenage girls.
As of August 13, 2025, HPV vaccinations are offered to most adolescents, boys, and girls in the United States.
The U.S. Department of State today updated its travel advisory for the Democratic Republic of the Congo (DRC) to Level 3 status.
As of August 12, 2025, this U.S. government Reconsider Travel advisory also includes Level 4 status for various areas in North and South Kivu of this African country.
Additionally, the U.S. government cannot provide emergency consular services to U.S. citizens outside of Kinshasa due to poor infrastructure and security risks. Due to the risks, personnel have limited mobility, and minor dependents cannot accompany U.S. government employees who work in the DRC.
Suppose you decide to travel to the DRC in late 2025. In that case, the State Department recommends enrolling in the Smart Traveler Enrollment Program to receive digital alerts from the U.S Embassy and make it easier to locate you in an emergency.
Separately, the U.S. CDC has included the DRC in two recent Travel Health Advisories targeting polio and measles outbreaks.
The CDC suggests international travelers speak with a vaccine advisor regarding routine and additional immunization options (chikungunya, cholera, and yellow fever) at least one month before departure.
Various retailers in the United States offer travel vaccine services.
Valneva SE announced today that it continues co-developing VLA15, a Phase 3 vaccine candidate, the only Lyme disease program in late-stage clinical development.
VLA15 is a multivalent recombinant protein vaccine that targets six serotypes of Borrelia, representing the most common serotypes found in the United States and Europe.
On August 12, 2025, Valneva confirmed its development partner, Pfizer Inc., is currently executing the randomized, placebo-controlled Phase 3 field efficacy study. The participants will be monitored for the occurrence of Lyme disease cases until the end of the 2025 Lyme disease season in the U.S. (end of October), with topline data expected as soon as all Lyme disease cases are confirmed.
In a press release, Valneva wrote that Pfizer aims to submit a Biologics License Application to the U.S. Food and Drug Administration and a Marketing Authorization Application to the European Medicines Agency in 2026, subject to positive Phase 3 data.
Lyme disease is the most common tickborne disease in the United States and Europe.
Lyme disease remains an expanding health risk in the U.S. It is a bacterial illness transmitted to humans through the bite of infected ticks. These ticks become infected by feeding on animals that carry the bacteria in their blood.
Over 89,000 cases of Lyme disease were reported to the U.S. CDC by state health departments and the District of Columbia in 2023. Recent estimates using other methods suggest that approximately 476,000 people may be diagnosed and treated for Lyme disease each year in the U.S.
The incidence of Lyme disease in Europe is highest in the Scandinavian and Baltic states in northern Europe and Austria, the Czech Republic, Germany, and Slovenia in central Europe.
The Florida Department of Health (FDH) today reported that additional locally-acquired and travel-related Dengue fever cases have been confirmed in various counties in 2025.
As of August 9, 2025, FDH confirmed ten locally acquired dengue cases (DEN-3, DENV-4) were reported in Miami-Dade (2) and Brevard (8) counties in 2025.
While several cities are located in Brevard County, Melbourne has the largest population at risk for this mosquito-transmitted disease, with over 87,000 residents.
To alert residents, DOH-Brevard has issued a Mosquito-Borne Illness Alert that is scheduled to be in effect through September 12, 2025.
Additionally, there have been 141 travel-related Dengue cases in Florida, most related to travelers from Cuba.
The FDH says Dengue infections can present as a flu-like illness with severe muscle aches and joint pain, fever, and sometimes a rash, and may appear within 15 days after being bitten by an infected mosquito.
Furthermore, Dengue fever is not contagious.
Currently, Dengue vaccines are unavailable in the continental U.S. However, Puerto Rico is testing a first-generation vaccine on children.
The NYC Health Department confirmed today it is investigating a community cluster of Legionnaires' disease in Central Harlem, New York City, New York.
As of August 11, there are 90 confirmed cases, three related fatalities, and 17 people are currently hospitalized with Legionnaires' disease in NYC.
The Health Department says the risk to most people in these ZIP codes (10027, 10030, 10035, 10037, and 10039) is low.
This community outbreak is not related to a building's hot or cold water supply. Residents in these ZIP codes can continue to drink water, bathe, shower, cook, and use their air conditioner.
The Health Department has sampled and tested water from cooling towers in the investigation zone. Any cooling towers with initial positive results for Legionella bacteria have completed the treatment required by the Health Department. We are continuing to monitor and let buildings know if additional treatment is needed.
A building plumbing system is separate from a cooling tower system.
If you live or work in the area and have flu-like symptoms, see a health care provider right away or visit NYC Health + Hospitals or call 311 or 844-NYC-4NYC (844-692-4692).
Legionnaires' disease is not spread from person to person. You cannot get Legionnaires' disease from someone who is sick. Symptoms include cough, fever, chills, muscle aches, and shortness of breath. Infected people usually develop symptoms 2 to 10 days after exposure, though it can be as long as two weeks.
As of August 12, 2025, there are no vaccines available to prevent this disease.
There is a global resurgence of chikungunya that started with increasing outbreaks in the Indian Ocean islands in March 2025, which has continued into mid-August.
According to the World Health Organization (WHO), these outbreaks mirror trends seen 20 years ago when a major outbreak began in the Indian Ocean before spreading globally and affecting nearly half a million people.
Recent estimates suggest that 5.6 billion people live in areas suitable for the spread of diseases carried by the Aedes mosquito, including chikungunya.
In the Region of the Americas, over 209,000 cases and three related fatalities have already been confirmed in 2025.
In the United States, Florida has reported four travel-related cases of chikungunya confirmed this year. The countries of origin were Bolivia, Brazil, Indonesia, and Sri Lanka.
Eleven instances of chikungunya were confirmed in Florida in 2024
To clarify how this mosquito-borne disease is transmitted during international travel, the WHO published a new Q&A on August 8, 2025, with information for the public on the disease, how it spreads, its symptoms, treatment, prevention, and more.
Additionally, the WHO and the U.S. CDC recommend that those traveling to an area reporting chikungunya cases speak with a travel vaccine expert regarding prevention options.
