It’s World Mosquito Day, and the U.S. ran out of yellow fever vaccine (sort of)

By Aileen M. Marty, M.D., FCAP

The mosquito is the world’s most lethal animal, a prolific killer. The World Health Organization estimates that every year 725,000 people die from mosquito-borne diseases.

August 20 is World Mosquito Day, which commemorates the date in 1897 when British doctor and Nobel Prize winner Sir Ronald Ross proved that female mosquitos transmit malaria. Of course, that was just the beginning. We would soon learn that mosquitos served as host for a whole host of diseases, and many mosquito-transmitted viruses have been spreading in recent years and causing new outbreaks thanks to constant human travel, trade and climate change.

But while here in the United States we have been worrying about dengue, West Nile virus and Zika, we have forgotten to worry about their most deadly cousin, yellow fever.

Like its name implies, yellow fever causes your skin, even the whites of your eyes to turn yellow. It causes nausea, and terrible body aches. There is no cure or specific treatment. Thankfully most people recover; however, for those who take a turn for the worse, it can be devastating. Yellow fever is a hemorrhagic fever, like Ebola, and it can cause bleeding, organ failure and death.

The first human illness recognized as viral, yellow fever was one of the earliest for which we developed an effective vaccine, and we thought we had it under control, but it is again rearing its ugly head.

Yellow fever cases have increased rather than decreased in the past several decades. In 2016, there was a huge outbreak in Angola and the Democratic Republic of the Congo that required 30 million doses of yellow fever vaccine and an entire year of hard work to get under control. This year’s yellow fever outbreak in Brazil has been the largest there since the 1940s.

Why is this happening?  Fewer people are immune, deforestation, urbanization, population migration, trade, travel, climate change and not enough vaccine.

Can we have an outbreak here in the U.S.?
The short answer is yes.  The yellow fever vaccine combined with extensive mosquito control efforts allowed us to eradicate yellow fever from the United States in the mid 20^th century, but it hasn’t been eradicated on a worldwide scale. And we don’t stay in one place. We travel and we trade. Like the mosquito, we help transport the virus.

That’s right, American travelers who do not get vaccinated for yellow fever not only place themselves at risk for this deadly infection when they visit areas with active transmission; they can unknowingly bring the virus back in their blood. Like Zika, many people with yellow fever have little or no symptoms and may have no idea they’re sick.  Since we have local mosquitos that can transmit the illness, if an infected traveler comes back to the United States and is bitten by one of these mosquitos, the possibility of an outbreak becomes very real and something we must seriously consider. Warmer temperatures are making this an even more serious threat by accelerating mosquito breeding.

Can’t we keep yellow fever out if we make sure everyone traveling to an affected area is vaccinated?
Yes, however, there is a critical vaccine shortage. The Centers for Disease Control has just announced that YF-VAX, the only yellow fever vaccine licensed in the U.S., is out of stock until 2018! In the meantime, the Federal Drug Administration is allowing the sale of an alternative vaccine, Stamaril, but it is only available at a few select travel health clinics nationwide.

What can we do? Not just the government, but individuals need to practice mosquito control.  Cover and spray yourself with repellent. Decrease your risk of exposure. Do not travel to an area where yellow fever is endemic without getting vaccinated.

From a global perspective, we must consider finding a faster way to produce the existing vaccine so that it is available to more people. We should consider adapting new gene-editing technologies such as CRISPR-cas9 towards finding a targeted cure for yellow fever. In the meantime, global teams must assess and respond to outbreaks rapidly and provide vaccine coverage to at least 80 percent of an affected population. We must develop better mosquito control methods. And, we must do what we can to reverse climate change because the rise in other mosquito-borne illnesses like chikungunya, dengue, malaria, La Crosse encephalitis, West Nile virus and Zika – all of which are rising largely because of warmer temperatures–means that yellow fever is on its way.

Dr. Aileen M. Marty is a professor at Herbert Wertheim College of Medicine. A world-renown infectious disease specialist, she is a member of the Presidential Advisory Council on Combating Antibiotic Resistant Bacteria, and chairs the medical group for MetroLab Network’s “Fight the Bite” project. Marty worked with the Florida Department of Health during the 2016 Zika outbreak in Miami-Dade County; and has worked with the World Health Organization in Europe, the Americas, and Africa–including the 2014 Ebola epidemic.