U.S. health officials on Tuesday warned doctors to be alert for dengue cases as the tropical disease breaks international records.

The virus, which is spread by mosquitoes, has been surging worldwide, helped by climate change. In barely six months, countries in the Americas have already broken calendar-year records for dengue cases.

The World Health Organization declared an emergency in December, and Puerto Rico declared a public health emergency in March.

Dengue remains less common in the continental United States, but in the 50 states so far this year there have been three times more cases than at the same point last year. Most were infections that travelers got abroad, and officials note there is no evidence of a current outbreak. But they also warn that local mosquitos pose a threat.

In its health alert Tuesday, the Centers for Disease Control and Prevention advised doctors to know the symptoms, ask questions about where patients recently traveled and consider ordering dengue tests when appropriate.

“Global incidence of dengue in 2024 has been the highest on record for this calendar year,” the CDC said in its advisory, adding that so far this year, countries in the Americas have reported more than 9.7 million cases, twice as many as the 4.6 million cases reported for the whole of 2023.

Often referred to as dengue fever or “break-bone fever,” due to pain being a major symptom, dengue (pronounced DEHN’-gay) is caused by a virus spread by a type of warm weather mosquito that is expanding its geographic reach because of climate change, experts say.

About 1 in 4 people infected with dengue will get sick, the CDC says, with symptoms ranging from mild to extreme. About 1 in 20 people who get sick will develop severe dengue, which can result in shock, internal bleeding and even death.

Repeated infections can be especially dangerous.

There are four types of dengue virus, simply known as 1, 2, 3 and 4. When someone is first infected, their body builds antibodies against that type for life. If they get infected with another type of dengue, the antibodies from the first infection may fail to neutralize the second type —and actually can help the virus enter immune cells and replicate.

That’s a concern in Puerto Rico, which for the last two decades has been widely exposed to type 1. Last month, the island reported its first dengue death of the year.

“We’re currently seeing is increases in the cases due to dengue 2 and dengue 3, for which the population has very little immunity,” said Dr. Gabriela Paz-Bailey, the Puerto-Rico-based chief of the CDC’s dengue branch.

There is no widely available medicine for treating dengue infections.

Vaccines have been tricky. U.S. officials in 2021 recommended one vaccine, made by Sanofi Pasteur. The three-dose vaccine is built to protect against all four dengue types and is recommended only for children ages 9 to 16 who have laboratory evidence of an earlier dengue infection and who live in an area —like Puerto Rico— where dengue is common.

Given those restrictions and other issues, it hasn’t been widely used. As of late last month, only about 140 children had been vaccinated in Puerto Rico since shots became available there in 2022, and Sanofi Pasteur has told the CDC it is going to stop making the vaccine.

A different vaccine made by the Tokyo-based pharmaceutical company Takeda is not currently licensed in the U.S. Others are in development.

Across the world, more than 6.6 million infections were reported by about 80 countries last year. In the first four months of this year, 7.9 million cases and 4,000 deaths have been reported, according to the World Health Organization. It’s been particularly intense in the Americas, including in Brazil and Peru.

In the United States, the numbers have been far more modest —about 3,000 cases last year in U.S. states and territories. But it was the worst in a decade, and included more infections that occurred locally, courtesy of native mosquitoes. Most were in Puerto Rico, but about 180 were in three U.S. states — Florida, Texas and California.

So far this year, there have been nearly 1,500 locally acquired U.S. cases, nearly all of them in Puerto Rico.

Sixteen of the world’s most notable economists — all Nobel Prize winners — are warning that former President Donald Trump could stoke inflation if he wins the presidency in November and moves forward with his economic plans. 

“Many Americans are concerned about inflation, which has come down remarkably fast. There is rightly a worry that Donald Trump will reignite this inflation, with his fiscally irresponsible budgets,” according to a letter signed by the economists, who include Joseph Stiglitz, a Columbia University professor who won the Nobel prize for economics in 2001; and Yale professor Robert Shiller, who won the Nobel prize for economics in 2013. 

The warning comes as the U.S. continues to battle sticky inflation, with the Federal Reserve maintaining the highest interest rates in more than two decades with the goal of cooling the economy and driving inflation down to a 2% annual rate. Even though inflation has cooled from a recent peak of 9.1% in June 2022, inflation-weary Americans are glum about the economy, with 6 in 10 rating it as either bad, fairly bad or very bad, according to the latest CBS News poll. 

Trump’s policies could prove to be inflationary, other economists also warned, such as his proposal to create a 10% across-the-board tariff on all imports to deporting immigrants. The tariff plan would add $1,700 in annual costs for the typical U.S. household, essentially acting as an inflationary tax, according to experts at the Peterson Institute for International Economics. 

Deporting immigrants could shrink the labor force, creating more competition for U.S. workers and pushing up wages, also adding to inflationary pressure, economists warn. 

While the letter from Stiglitz and the other 15 Nobel Prize winners didn’t detail the specifics of any part of Trump’s plans, it did single out praise for some of President Joe Biden’s economic policies, ranging from his Inflation Reduction Act to investment in U.S. manufacturing. 

“In his first four years as President, Joe Biden signed into law major investments in the U.S. economy, including in infrastructure, domestic manufacturing and climate,” the letter said. “Together, these investments are likely to increase productivity and economic growth while lowering long-term inflationary pressures and facilitating the clean energy transition.”

They added, “While each of us has different views on the particulars of various economic policies, we all agree that Joe Biden’s economic agenda is vastly superior to Donald Trump’s.”

“Top economists, Nobel Prize winners, and business leaders all know America can’t afford Trump’s dangerous economic agenda,” Biden campaign spokesperson, James Singer, told CBS MoneyWatch.

 “In Donald Trump’s America, the rich pay less, and working Americans pay more,” he added.

“The American people don’t need worthless out-of-touch Nobel Prize winners to tell them which president put more money in their pockets,” Trump campaign national press secretary Karoline Leavitt said in an emailed statement to CBS MoneyWatch.

If re-elected, Trump plans to implement a “pro-growth, pro-energy, pro-jobs agenda to bring down the cost of living and uplift all Americans,” she added.

“We the undersigned”: Read the letter

You can read the text of the letter below:

We the undersigned are deeply concerned about the risks of a second Trump administration for the U.S. economy. 

Among the most important determinants of economic success are the rule of law and economic and political certainty. For a country like the U.S., which is embedded in deep relationships with other countries, conforming to international norms and having normal and stable relationships with other countries is also an imperative. Donald Trump and the vagaries of his actions and policies threaten this stability and the U.S.’s standing in the world. 

While each of us has different views on the particulars of various economic policies, we all agree that Joe Biden’s economic agenda is vastly superior to Donald Trump’s. In his first four years as President, Joe Biden signed into law major investments in the U.S. economy, including in infrastructure, domestic manufacturing, and climate. Together, these investments are likely to increase productivity and economic growth while lowering long-term inflationary pressures and facilitating the clean energy transition. 

During Joe Biden’s presidency we have also seen a remarkably strong and equitable labor market recovery — enabled by his pandemic stimulus. An additional four years of Joe Biden’s presidency would allow him to continue supporting an inclusive U.S. economic recovery. 

Many Americans are concerned about inflation, which has come down remarkably fast. There is rightly a worry that Donald Trump will reignite this inflation, with his fiscally irresponsible budgets. Nonpartisan researchers, including at Evercore, Allianz, Oxford Economics, and the Peterson Institute, predict that if Donald Trump successfully enacts his agenda, it will increase inflation. 

The outcome of this election will have economic repercussions for years, and possibly decades, to come. We believe that a second Trump term would have a negative impact on the U.S.’s economic standing in the world and a destabilizing effect on the U.S.’s domestic economy. 

Signed, 

George A. Akerlof (2001) 

Sir Angus Deaton (2015) 

Claudia Goldin (2023)

Sir Oliver Hart (2016) 

Eric S. Maskin (2007) 

Daniel L. McFadden (2000) 

Paul R. Milgrom (2020) 

Roger B. Myerson (2007) 

Edmund S. Phelps (2006) 

Paul M. Romer (2018) 

Alvin E. Roth (2012) 

William F. Sharpe (1990) 

Robert J. Shiller (2013) 

Christopher A. Sims (2011) 

Joseph E. Stiglitz (2001) 

Robert B. Wilson (2020)