Dengue, a mosquito-borne virus, is on the rise after entering Los Angeles County. While locally acquired dengue is uncommon and rare, there have been four total cases of local transmission, three cases reported in the City of Baldwin Park on September 18 and one case reported in Panorama City on September 25, according to the LA County Department of Public Health.
Four cases may seem low; however, those infected “had no history of travel to places where dengue is common,” according to the LA County Department of Public Health. Locally acquired cases in the continental United States total to 37 in 2024 so far. Florida has reported 33 cases and California has reported four. Cases associated with travel total to 1,904 in the continental United States with 79 of those in Los Angeles County.
Still, USC’s Chief Health Officer Dr. Sarah Van Orman said students shouldn’t be overly concerned as the four cases were not near University Park.
“The good news is right now we’re looking at these places that are not within the area around campus, nor is it in the areas that students frequent,” Van Orman said. “But it’s a good reminder for everyone to avoid mosquito bites.”
Dengue virus, like many mosquito-borne viruses, is easily transmissible. When an infected mosquito bites a human, the human hosts the virus, and any future mosquito that bites the infected human begins to carry the virus, too, making it a highly contagious cycle, according to the Centers for Disease Control and Prevention. Adding to its transmissibility, once a mosquito carries the dengue virus, it has the ability to transmit the virus for the rest of its lifespan, according to the World Health Organization.
“What we know is that one in four people who are infected are symptomatic. So they’ll be ill and they’ll show symptoms, and then the other three don’t show symptoms at all,” Van Ngo, a Supervising Epidemiologist for Los Angeles County, said. “A lot of the illness that manifests is mild and can be confused with other things. People just won’t go to the doctor and get tested. So, there is, there’s a lot of unknown disease out there.”
Symptoms include eye pain, headaches, muscle, bone or joint pain, nausea or vomiting and a rash according to the Los Angeles County Department of Public Health. When caught early, the virus can be easily treated with proper medical care. Rare cases of severe symptoms do occur and may lead to death.
The City of Baldwin Park belongs to the San Gabriel Valley. In response to the recent cases the San Gabriel Valley Mosquito and Vector Control District has ramped up its routine. “District staff has expanded surveillance by deploying additional traps and increased the frequency of testing to identify the presence of mosquito-transmitted diseases in local mosquito populations,” according to the San Gabriel Valley Mosquito and Vector Control District.
Dengue has commonly been found in humid and tropical areas, but rises in temperature may lead to an increase in cases.
Van Orman agreed, noting that aedes mosquitoes — the species that carry dengue — are an invasive, non-native species to California that are likely here because of increasing temperatures worldwide.
“As we see climate change, we’re going to see changes in the range of these types of mosquitoes,” Van Orman said. “That then can raise this risk for local transmission of diseases that we’ve never had before, primarily because we’ve never had these mosquitoes.”
Ngo added that this can also change the habits of insects.
“Weather does impact the way that mosquitoes breed and also how the virus develops inside the mosquito,” Ngo said.
The virus travels after a mosquito has bitten a person. When caught early, the virus can be easily treated with proper medical care however there are some rare cases of severe symptoms, and at times, death. The four individuals who contracted the dengue virus have recovered according to Ngo.
As of now there is no vaccine for the dengue virus but there are still means of prevention. The San Gabriel Valley Mosquito and Vector Control District is urging residents to implement Tip, Toss, and Protect as means of prevention.
Mosquitoes breed in standing water, so tip out any standing water, toss unused containers that may collect water and protect yourself with repellents. The best repellents to use are ones that include active ingredients approved by the U.S. Environmental Protection Agency such as DEET or Picaridin.
Van Orman generally advised avoiding mosquito bites as the best prevention method. Students should wear long pants and sleeves if traveling to areas where mosquitoes are common, and make sure their window screens are tight-fitting and closed if in areas of high mosquito activity.
The best course of action is to be aware. “I wouldn’t say that we have an increase. It is more of an emergence because we haven’t had before. I think it’s just something that, it’s an additional thing that people you know should be aware of but the mosquito borne disease concerns have always been the same,” said Ngo.