2024 dengue fever outbreaks, dengue fever symptoms, new research on avian flu in cattle, state fair safety

AMA Update covers a variety of medical topics that impact the lives of physicians, residents, medical students, and patients. From private practice physicians and health system leaders to scientists and public health officials, we hear from medical experts about COVID-19, medical education, advocacy issues, burnout, vaccines, and more.

What is dengue fever? Is dengue fever fatal? How long does dengue fever last? Can you die from dengue fever? Is dengue fever prevalent in Florida? Also, latest updates on Avian Flu 2024.

Our guest is Andrea Garcia, JD, MPH, AMA's vice president for science, medicine and public health. Todd Unger, AMA's chief experience officer, will host the event.

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• Andrea Garcia, JD, MPH, Vice President for Science, Medicine, and Public Health, American Medical Association

Anger: Hello and welcome to the AMA Update video and podcast. Today, we're covering the weekly headlines with Andrea Garcia, AMA's vice president of science, medicine and public health. I'm Todd Unger, AMA's chief experience officer. Good to see you again, Andrea.

Garcia: I'm glad to meet you too.

Anger: Now, in recent weeks, we've been talking a lot about how climate change is causing extreme temperatures and the health impacts of this heat. But this week, there's a new issue that's sparking concern and headlines, and that's dengue fever. Andrea, can you tell us what's going on there?

Garcia: Todd, last week, the CDC issued a health advisory (HAN) to physicians, public health officials, and the public warning of an increased risk of dengue virus infection in the U.S. this year. This was issued in response to the alarming number of cases already identified overseas in the first six months of 2024.

Countries in the Americas have reported more than 9.7 million cases of dengue fever, double the number reported in all of 2023. And in the United States, Puerto Rico declared a public health emergency this spring after more dengue cases were reported in the first five months of 2024 than in all of last year, during the dry season when dengue cases are at their lowest.

Anger: Andrea, have you seen any cases like this stateside?

Garcia: The CDC says there is currently no evidence of dengue in the continental U.S., but travel-related cases have been identified, and since January, 745 cases of dengue have been confirmed among U.S. travelers who became infected overseas.

This is higher than expected for this time of year, given that dengue cases usually rise during the warmest months of the year, but that hasn't happened yet. Public health officials expect the virus to be seen in warmer areas, including the far southern United States. The mosquito that causes dengue has been identified in several states, including Texas, Florida, and California. Florida has already reported 10 cases of localized spread in four counties so far this year.

Anger: So we're not necessarily talking about heat, but this is a consequence of climate change, so to speak. Andrea, in terms of how it's transmitted, we know that dengue is transmitted by mosquitoes. Can you elaborate a little bit on that mechanism?

Garcia: Dengue fever is spread primarily through the bite of infected Aedes mosquitoes, such as Aedes aegypti, but can also be spread by Aedes albopictus.

Travelers who become infected abroad can bring the virus back to their home region and transmit it to others through local mosquito bites. According to the WHO, dengue fever is one of the most neglected tropical diseases in the world. The disease is very difficult to track, as three out of four cases are mild or asymptomatic.

Anger: I don't think you mean 10 years when you say “Aedes.” For those of you who haven't heard the term, it's “AEDES.” Andrea, can you tell us about the severity of the cases that we're seeing right now?

Garcia: So while most cases are not serious, some severe cases can lead to internal bleeding, organ failure, and even death.The infection usually begins after an incubation period of about 5-7 days, starting with a fever, followed by other symptoms such as nausea, vomiting, rash, muscle, joint and bone pain, pain behind the eyes, headache, and low white blood cell count.

While with other illnesses, the subsidence of fever is a sign of recovery, with dengue this is the beginning of the critical phase, which usually lasts 24-48 hours. There are several warning signs that indicate progression to serious illness: abdominal pain or tenderness, persistent vomiting, bleeding from the nose or gums, lethargy or restlessness.

About 1 in 20 people who have dengue symptoms will become seriously ill, and infants, pregnant women, adults over 65 and people with certain medical conditions are at higher risk.

Anger: Okay. Andrea, do you know what's causing this dramatic increase in cases?

Garcia: Well, as you briefly mentioned, this is probably another byproduct of climate change, as rising global temperatures have accelerated the life cycle of the mosquito that causes dengue fever, expanding its range and spreading the virus to roughly 1 in every 800 people on the planet in the last six months alone.

But rising temperatures are not the only cause. Climate-induced droughts encourage people to stockpile water, creating more habitat for mosquitoes. They also intensify hurricanes and floods, creating standing water and forcing people out of their homes, increasing their exposure to mosquitoes. The Washington Post article points out that research suggests that unless drastic measures are taken to suppress the virus and slow climate change, an additional 2 billion people around the world could be at risk of dengue over the next 50 years.

Anger: Well, those are pretty incredible numbers. And like you said, the symptoms, especially the severe side of it, are not good. Is there any treatment?

Garcia: Unfortunately, there are no antiviral drugs approved to treat dengue, and no vaccine for adults or people who have never had dengue. The only vaccine approved for use in the United States is for children ages 9 to 16 who have had dengue and who live in areas where dengue is transmitted frequently or persistently.

Think American Samoa, Puerto Rico and the U.S. Virgin Islands. But supplies of that vaccine are expected to run out after August 2026 as manufacturers stop producing it due to low demand. In May, the WHO expanded use of a second vaccine, but its manufacturer withdrew its application to the FDA last summer due to data collection issues.

There is a third vaccine being developed by the NIH. It is still in clinical trials and will be at least a few years before it is available in the United States. I also think it is worth noting that the disease is complicated because it is caused by four different but closely related dengue viruses. Infection with one dengue virus usually confers lifelong protection against infection with that particular virus, but only partial and short-term protection against others. There is also some evidence to suggest that successive infections with different types of the virus may increase the risk of serious complications.

Anger: So, Andrea, what should doctors do in response to this latest development?

Garcia: So the CDC is urging doctors to be on the lookout for dengue in people who have a fever and have been in a dengue-infected area within 14 days of onset of symptoms, even though doctors are likely less aware of it because the disease is easily overlooked and dengue is not a problem here.

If your doctor suspects dengue, they should order the appropriate diagnostic tests for acute dengue infection and, of course, report the case to public health authorities. We can also do our part by using EPA-certified insect repellents and wearing loose-fitting, long-sleeved pants and shirts to prevent mosquito bites in the first place. The CDC also recommends using air conditioners and window screens when possible, and dumping water-filled containers outdoors to drain them. And be sure to see a doctor if you develop symptoms.

Anger: Okay. This is a great update and all good information as we head into the hot weather. Andrea, let's switch gears a little bit and just quickly check in on avian flu. Is there anything new happening?

Garcia: Well, the number of cases continues to rise. Last week, 118 flocks in 12 U.S. states were reported to have avian flu. This week, that number has risen to 132. As we head into the holiday weekend, I thought it was worth briefly talking about agricultural fairs.

Millions of people attend fairs in the United States every year, especially around the Fourth of April and throughout the summer. CDC recommendations for fairs previously focused on reducing the risk of swine-origin influenza viruses spreading between pigs and humans. These recommendations now also apply to cattle. The best thing people can do is to avoid contact with animals at these fairs and remember to wash their hands frequently.

Anger: Okay. I've also read some new research that's promising news for containing the virus. Andrea, can you tell me a bit more about that?

Garcia: One of the big questions scientists are grappling with is how the virus spreads from animal to animal. The New York Times recently published a detailed article about small-scale experiments in Kansas and Germany that provided new information. However, it's important to note that these findings have not yet been posted online or published in a peer-reviewed journal.

But what the experiment showed was that the virus was mainly transmitted through contaminated milking machines – and while this would certainly pose logistical problems for dairy farmers, it would mean that the virus would be easier to contain than if it were spread through respiratory droplets.

Scientists involved in the study say the research offers hope that, in theory, it's possible to stop the virus from spreading before it evolves into a form that can easily spread between humans. But of course, there are caveats: The results come from two experiments with very small numbers of cows.

Scientists are also studying earlier lineages of the virus, and we know that the virus mutates as it moves from animal to animal, and researchers don't know if the more recent lineages will behave like a respiratory disease. But, Todd, this is definitely something we'll continue to keep an eye on.

Anger: So yeah, that's something we're going to continue to monitor closely over the next few weeks. Andrea, that's it for this week. I want to thank you again for being here and sharing this important information.

We also want to give you a lot of updates on vaccines following last week's meeting of the CDC's Advisory Committee on Immunization Practices, which we'll discuss in more detail on Monday with Dr. Sandra Fryhofer, the AMA's liaison to ACIP. Please tune in.

If you found this discussion useful, you can become an AMA member to further support similar programs. ama-assn.org/participateDue to the Fourth of July holiday, this will be our last episode until Monday, but of course all of our videos and podcasts are always available. ama-assn.org/podcasts.

Enjoy your Independence Day holiday, be safe if you are out and about, and take care.

Disclaimer: The perspectives expressed in this video are those of the participants and do not necessarily reflect the views or policies of the AMA.