New Year’s optimism often spurs pledges of healthier choices, but reasons for pessimism about America’s health this year persist.
Childhood vaccination rates are on the decline, and school vaccination requirement exemptions are on the rise – fostering more opportunities for dangerous infectious diseases to spread.
The trends were already in motion before Robert F. Kennedy Jr. took over as secretary of Health and Human Services, but public health experts worry they will worsen given the steps Kennedy has taken to sow doubts about the safety and effectiveness of vaccines and reduce the number of recommended shots for children.
“I think it’s going to get worse before it gets better,” says Michael Moody, a pediatrics professor at Duke University School of Medicine.
Pools of unvaccinated or undervaccinated people create perfect conditions for infectious diseases – many of which Americans haven’t seen firsthand in their lifetimes.
“The fact that people haven’t seen these diseases often makes us kind of romanticize them,” Moody says. “You sort of forget what they look like.”
Effective vaccines and high vaccination coverage have kept these diseases at bay. But the picture that will emerge if vaccination rates drop too far isn’t pretty.
“I do think that we are victims of our own success,” Moody says. “I fear that we’re going to have to see some really bad outcomes for people to kind of wake up to the fact that we made these vaccines for a reason and they’re actually beneficial.”
Here are five infectious diseases to keep an eye out for in 2026:
Flu
Flu season is already well underway, with a new variant fueling the spread.
The Centers for Disease Control and Prevention estimates at least 15 million cases, 180,000 hospitalizations and 7,400 deaths from flu so far this season – including 17 pediatric deaths.
“Last year was actually a pretty significant flu year,” Moody says. “I think initially we were hoping that this year might be quieter, but if anything, I think it’s shaking up to be pretty similar to last year.”
Less than 50% of children have gotten a flu shot this year, according to CDC data. It’s a lower rate than this point in any of the previous six seasons.
Until recently, the CDC recommended the annual flu vaccine for everyone age 6 months and older. Now, flu shots – as well as shots for respiratory syncytial virus, meningococcal disease and COVID-19 – are only recommended for children at high risk of serious illness, or after consultation between doctors and parents. The move was made over the objections of the broader medical community.
“At a time when parents, pediatricians and the public are looking for clear guidance and accurate information, this ill-considered decision will sow further chaos and confusion and erode confidence in immunizations,” Andrew Racine, the president of the American Academy of Pediatrics, said in a statement. “This is no way to make our country healthier.”
Last flu season was the deadliest for U.S. children in more than a decade, with 280 fatalities.
Measles
The U.S. reported over 2,000 measles cases in 2025 – the highest annual total in decades and by far the most since the disease was declared eliminated in the country in 2000.
“This is a vaccine that has been studied for decades and decades, and it’s a real gift to humanity,” says Derek Cummings, an epidemiologist at Johns Hopkins Bloomberg School of Public Health. “It’s prevented millions and millions of deaths over decades.”
Polio
Public health experts are concerned about polio – a paralyzing, potentially fatal virus – returning to the U.S.
It was eliminated in the U.S. due to the polio vaccine, but vaccination rates are on the decline and Kennedy has voiced doubt about the shots, going as far as to misleadingly suggest polio vaccines caused cancer in his generation “that killed many, many, many, many more people than polio ever did.”
Polio is still prevalent in Pakistan and Afghanistan. As long as it is spreading anywhere, it could cause outbreaks in the U.S. among children who aren’t fully vaccinated.
“That’s the one I worry about the most because it’s out there,” Moody says. “It’s easily transmissible.”
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Disease X
Disease X is not a virus that is circulating. It is a placeholder name for a hypothetical disease that could spread and cause epidemics or a pandemic.
The goal of such a placeholder is to encourage public health officials and scientists to think about what will cause the next outbreak.
“We are preparing for the future,” Ana Maria Henao Restrepo of the World Health Organization said in a 2024 podcast. “Scientists call it Disease X to prepare for the hypothetical virus or bacteria that in the future can cause large outbreaks or epidemics or pandemics.”
But steps taken by the Trump administration, including scaling back public health data and defunding mRNA vaccine research, have public health experts concerned the U.S. would not be ready for another pandemic. They emphasize that preparing for the next one is of the utmost importance because another pandemic isn’t a question of if – it’s a question of when.
Bird Flu
The CDC says there is currently a low public health risk from bird flu, though it states it “is watching the situation carefully and working with states to monitor people with animal exposures.”
Person-to-person transmission of bird flu has not been documented in the U.S. However, it’s widespread in wild birds worldwide and is causing outbreaks in poultry and dairy cows, with sporadic human cases in U.S. dairy and poultry workers. The CDC has documented over 70 cases in humans and two deaths since 2024.
“It is concerning that these viruses are not only affecting birds but infecting cows and other species,” Cummings says. “That species breadth is a hallmark of a dangerous pathogen that could emerge.”
