Mosquito-borne illness is surging in Long Beach. We asked experts why and how to protect yourself

During a summer in which West Nile virus has jumped to record levels statewide, 17 Long Beach residents have contracted the mosquito-borne illness — far surpassing this time last year and the highest in more than a decade, according to the city’s health department.

Cases have been unusually severe: 69% involved neuroinvasive West Nile, the form that attacks the brain or nervous system, and 81% of those infected required hospitalization.

The first cases surfaced in late June, but officials detected mosquitoes carrying the disease as early as May, a sign the season — which typically runs July to October — may be stretching longer than usual. Health officials expect infections to continue through early fall, typically peaking in September.

This comes after repeated years of virtually no infections seen in the city. Last year there was one human case of West Nile citywide, with zero cases in 2024, one in 2023 and four in 2022.

Since the disease was first detected here in 2003, the number of cases has reached double digits in 2015, 2017 and a high of 56 cases in 2014.

Dr. Cliff Okada, Long Beach’s city health officer, said the virus tends to fluctuate unpredictably from year to year. “I can’t really give you a straight answer as to why this number is so high this year,” he said, but cited climate change and rising temperatures as potential factors, as well as improved surveillance locally.

With the exception of a high concentration of cases in the 90803 ZIP code, Dr. Okada said infections are dispersed fairly evenly citywide. He didn’t want to reveal locations as it would create the impression that some parts of the city “are more dangerous than others.”

Three agencies share responsibility for mosquito control in the city: the Los Angeles County Vector Control District covers the northern and eastern areas, and Long Beach’s own district manages the remainder.

Suzanne Kluh of the Greater Los Angeles County Vector Control District, which handles parts of North Long Beach as well as some of the city’s eastern neighborhoods, attributed much of the surge to the “warmest winter on record,” followed by a punishing summer heat wave.

It’s really just a numbers game. Those conditions, paired with unusually high humidity, have made it ripe for mosquitoes to multiply. A decline in bird immunity over the past five or six years has compounded the problem, since the virus circulates primarily between birds and mosquitoes before spreading to people.

In response, workers have intensified efforts to kill down the number of Culex mosquitoes — the species responsible for local transmission — by targeting the larvae that fester in storm drains, street gutters and smaller estuaries like marshes and ponds.

They’ve also tried to disperse or move crow roosts, such as one at El Dorado Park, so as to limit the spread among birds that later forage in nearby neighborhoods. Even so, mosquitoes are resourceful.

“They’ll breed in a bucket if it has enough water in somebody’s backyard,” Kluh said

The outbreak in Long Beach mirrors a broader spike across Los Angeles County and California. The county, whose case count excludes Long Beach and Pasadena, reported 15 cases and its first death of the year on Aug. 20.

“This tragic loss is a reminder of the serious threat posed by mosquito-borne diseases, including West Nile virus and dengue,” said Dr. Muntu Davis, the county’s health officer. He urged residents to take basic precautions.

Statewide, West Nile activity has reached a five-year high, with 65 human cases and five deaths confirmed across 16 counties as of Aug. 28, according to the California Department of Public Health. Since 2003, the state has recorded more than 8,000 cases and over 400 deaths, making it California’s most common and serious vector-borne disease.

How to recognize West Nile symptoms

West Nile is transmitted to humans by infected mosquitoes; symptoms typically include fevers, headaches or stomach pain, which generally pass after a few days. The virus can be fatal for those with weaker immune systems, particularly the elderly.

Most infections go unnoticed — about 80% of people show no symptoms — but in about one in 150 cases, the virus turns serious, causing brain inflammation, meningitis, encephalitis or paralysis. There is no vaccine or specific treatment.

Those over 55 and people with diabetes, high blood pressure, chronic kidney disease or weakened immune systems face the highest risk, and officials urge anyone with a high fever, stiff neck, confusion or muscle weakness to seek care immediately.