What You Need To Know About The Mosquito-Borne Virus Found In Arizona

Topline

Arizona health officials this week reported a case of dengue fever they believe was acquired locally rather than from travel, possibly joining Florida as the only state to record local transmission of the virus this year, which is rare in the U.S. but known to cause occasional outbreaks.

Female Aedes aegypti mosquitoes are carriers of the Dengue fever, which was found in Arizona.

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Key Facts

Dengue, also known as breakbone fever for the severe muscle pain it causes, is a mosquito-borne virus that infects around 400 million people each year.

Around half of the world’s population live in areas that carry a risk of dengue and outbreaks occasionally occur in the continental U.S., where the local spread of disease is possible as the mosquito carrying the disease is common throughout many areas.

The vast majority of dengue infections are asymptomatic or mild—around 1 in 4 (25%) people infected will get sick—and flu-like symptoms like fever, rash, headache, nausea and vomiting often mean it is confused with other illnesses.

Around 1 in 20 of the people who get sick will develop severe dengue, a potentially fatal medical emergency that can cause severe muscle pain, shock, internal bleeding and organ damage.

There is no specific medicine to treat dengue and for most people the disease will go away on its own after a week and can be managed with rest, keeping hydrated and fever reducers and painkillers like acetaminophen (also known as paracetamol and sold under brand names like Tylenol and Panadol), though blood thinning drugs like aspirin and ibuprofen should be avoided.

Without proper medical treatment, the mortality rate of severe dengue can be as high as 20%, though access to care can lower the fatality rate to below 1% and maintaining the patient’s body fluid volume is critical.

News Peg

A case of dengue was reported in a person in Maricopa County, Arizona, this week. Officials believe the infection may have been acquired locally, rather than through travel, and experts are working to trace the source and determine whether others in the area are at risk. Though dengue is not an unknown entity in the U.S. and conditions make outbreaks possible, the vast majority of cases are linked to travel and Arizona, which has recorded 10 other cases through November 2, is just the second state to record a locally acquired infection this year. Florida, the only other state to report locally acquired cases, has reported more cases than all other states put together, recording 582 infections linked to travel and 32 locally acquired infections through November 2, according to the CDC.

Big Number

888. That’s how many dengue cases have been reported in the U.S. this year through November 2, according to the CDC.

Key Background

Dengue is a leading cause of illness and death in many parts of the world, particularly in some Asian and Latin American countries, the World Health Organization says. Cases have risen sharply in recent decades—eightfold over the past 20 years—though part of the alarming rise can be explained by improved reporting practices. Global dengue cases appear to have fallen during the Covid-19 pandemic and research suggests pandemic curbs prevented some 750,000 cases in 2020. However, the issue is far from settled and the WHO notes that data is not yet complete for the years and said the pandemic may have hampered reporting efforts in some countries. The issue of dengue’s prevalence is of renewed importance as world leaders struggle to address the growing climate crisis, which could help the mosquitos carrying the disease make inroads into new parts of the world. Changes to weather and flooding, such as that in Florida after Hurricane Ian, also pose challenges for preventing the spread of disease. The mosquitos that can carry dengue—as well as a host of other pathogens like West Nile—can multiply rapidly in floodwater and debris left behind after major storms and pose a major public health threat to those recovering from disaster.

Surprising Fact

There are four distinct, though closely related, types of virus that cause dengue. Recovery is thought to provide lifelong immunity against that particular variant but, counterintuitively, increases the risk of developing severe disease if infected again. Until recently, the issue was a contentious topic among scientists, though many now believe the usually protective antibodies developed after infection can actually help the virus when infected again.

What To Watch For

The increased risk of severe disease when exposed to dengue a second time has complicated efforts to develop a vaccine. Sanofi Pasteur developed the first dengue vaccine, which is now licensed in numerous countries, including the U.S. The shot is only used in those who have already had a confirmed dengue infection, however, as it was found to increase the risk of severe dengue. Other vaccines are being evaluated. Qdenga, a shot developed by Japan’s Takeda for use without prior dengue exposure, appears promising and was approved in Indonesia in August.