As winter continues to take hold across the United States, respiratory viruses are making an alarming comeback, overwhelming healthcare systems nationwide. With flu and RSV (respiratory syncytial virus) at record high levels, the country is facing a surge that has left emergency departments strained. While COVID-19 cases remain relatively low for now, experts warn that a spike is inevitable. Here’s a deep dive into the latest data and expert insights on the respiratory virus surge.
Flu and RSV lead the charge
Hospitalization rates for flu and RSV have soared in recent weeks, with flu activity peaking as the dominant respiratory threat. According to the latest data from the Centers for Disease Control and Prevention (CDC), more than 26,000 people were admitted to hospitals with influenza by the end of December 2024, a significant rise from the previous weeks. At the same time, RSV admissions are also climbing, although at a slightly slower rate.
“Most of the current surge is being driven by high influenza activity as well as RSV,” says Peter Chin-Hong, MD, an infectious disease expert at the University of California, San Francisco. He adds, “RSV came first in November, followed by influenza in December. RSV is possibly at its peak now and being overtaken by influenza as the respiratory virus driving emergency department visits and hospitalizations nationally.”
Testing and wastewater surveillance: key indicators
While flu and RSV have been the primary culprits of this wave, COVID-19 remains a lurking concern. Test positivity rates for flu surged to nearly 19% by late December, a stark increase from the previous week’s 13%. Meanwhile, RSV’s test positivity rose to 12.8% from 10.7%. COVID-19 test positivity remains relatively low, but experts are keeping a close eye on wastewater data, which has shown rising levels of viral activity for COVID-19. Wastewater testing can often signal a rise in infections before they appear in clinical cases, giving public health officials a vital early warning.
“You’re likely to see upticks [of viral activity] in wastewater measurements sometimes several weeks before you actually observe an increase in clinical cases,” explains Dean Winslow, MD, a professor of medicine at Stanford University. “COVID-19 hit a low point in November, but as wastewater shows it may pick up again.”
Regional variability in viral activity
While respiratory illnesses are affecting the entire country, some states are experiencing more severe surges than others. As of now, ten states—Arizona, Florida, Georgia, Kansas, Kentucky, New Hampshire, Oklahoma, Tennessee, Texas, and Utah—are reporting exceptionally high levels of flu and RSV activity. However, this pattern could shift. As Erica Prochaska, MD, a pediatric infectious diseases specialist at Johns Hopkins Children’s Center notes, “I don’t see a common thread as to why these states in particular are seeing the highest levels of activity.” Prochaska adds that lower-activity states may see a rise in cases in the coming weeks as the virus continues to spread.
Symptoms: similarities and differences
One of the challenges in managing respiratory illness outbreaks is distinguishing between flu, COVID-19, and RSV, as their symptoms overlap significantly. All three viruses commonly cause cough, congestion, and fatigue, but there are key differences to note. RSV often leads to wheezing, which can be a distinguishing feature, while COVID-19 typically causes more severe fatigue and sore throat.
As the National Foundation for Infectious Diseases points out, healthcare providers often rely on testing to definitively diagnose these illnesses. “It can be difficult to distinguish between illnesses caused by these respiratory viruses,” says the NFID. Understanding which virus is responsible can help doctors determine appropriate treatments, such as antiviral drugs for flu or COVID-19.
Protecting the vulnerable
Certain groups remain particularly vulnerable to severe illness from respiratory viruses, including older adults, young children, and those with weakened immune systems. Recent data from the CDC shows that adults aged 65 and older have the highest hospitalization rates for flu, followed by adults aged 50 to 64 and young children under 5. RSV, too, is taking a toll on children, though there has also been a notable rise in hospitalizations among older adults.
To mitigate the spread of these viruses, public health authorities emphasize the importance of preventative measures. The American Lung Association recommends practices such as frequent hand washing, covering coughs, staying home when sick, and cleaning shared surfaces. Additionally, wearing a mask in crowded settings can help reduce the transmission of airborne viruses.
Vaccination: a powerful tool
As the respiratory virus season intensifies, vaccination remains one of the most effective strategies for preventing severe illness. Both flu and COVID-19 vaccines have proven to significantly reduce the risk of hospitalization and death. Chin-Hong stresses the importance of getting vaccinated, especially for at-risk populations, saying, “There is still time to get vaccinated. Influenza in particular has a long tail of infection that can extend into April. COVID is famously unpredictable so it may still emerge later in the season — I would vaccinate now if unvaccinated this year, especially for those who are older than 65 and/or immunocompromised.”
Though the virus surge continues to evolve, staying up to date on vaccines and following basic health precautions can dramatically reduce the risk of severe illness.
Staying prepared amid the surge
With respiratory viruses on the rise across the U.S., it’s more important than ever to remain vigilant. The flu and RSV are currently the primary threats, but COVID-19 remains a concern as wastewater data suggests a potential increase in cases. As always, practicing preventive health measures and ensuring vaccinations are up to date will be crucial in navigating this challenging virus season. Keeping informed and following the guidance of public health experts is the best way to protect yourself and your community during these peak months.