Multiple viruses overlapping this spring
Flu, Covid-19 and several other respiratory viruses remain in circulation across the United States, alongside a persistent norovirus outbreak that has left many Americans sick. Health experts say the overlap of illnesses makes it nearly impossible to determine which virus is responsible without testing, as symptoms often look the same: cough, congestion, fever and body aches.
“Unfortunately, there is not really a distinct trait between these respiratory illnesses,” said Dr. Greeta Sood, an epidemiologist at Johns Hopkins Bayview Medical Center. Loss of taste and smell, once common with Covid, is no longer a reliable signal.
While respiratory activity is generally lower than in peak winter months, certain states continue to report moderate levels of illness, and wastewater monitoring shows that multiple viruses remain active.
Covid-19 and variant BA.3.2
A newer Covid variant, BA.3.2, sometimes nicknamed “cicada,” has been detected in wastewater and nasal samples across dozens of states. Experts note that its spike protein mutations could allow it to partially evade immunity from prior infection or vaccination.
“This variant is very immunologically distinct compared to previous variants,” Sood said, adding that it remains unclear whether it will drive a new wave of cases.
So far, BA.3.2 accounts for a small share of sequenced samples nationwide. Overall Covid levels remain low, though some states have reported modest increases. Public health specialists emphasize that trends vary significantly by region.
Influenza trends easing but not gone
This flu season began with a surge of Influenza A, particularly the H3N2 “subclade K” strain, which peaked between late November and early January. Cases have declined steadily since then, though influenza A still accounts for most infections.
Influenza B activity shows mixed signals, with some states reporting increases. Pediatric deaths have been recorded this season, though totals remain below last year’s historic highs.
Experts say vaccination can still provide protection, especially for individuals planning travel or those at higher risk of complications.
RSV remains stubbornly elevated
Respiratory syncytial virus, or RSV, typically peaks earlier in the season and then declines. This year, however, levels have plateaued rather than dropping sharply. Wastewater data indicates moderate to high circulation in several states.
“What is abnormal about RSV right now is that it’s not going down as much as we would expect,” Sood said. Some health authorities continue recommending preventive antibodies for newborns in areas where RSV remains elevated.
HMPV and other respiratory viruses
Human metapneumovirus, or HMPV, a virus related to RSV, is also circulating at expected seasonal levels. It tends to peak in mid-spring and produces symptoms similar to a common cold.
Experts stress that monitoring local data, including wastewater surveillance, can offer clues about which virus may be most prevalent in a given area.
Norovirus still causing outbreaks
Unlike respiratory viruses, norovirus affects the gastrointestinal system and causes sudden vomiting and diarrhea. The illness typically lasts one to three days but spreads easily in crowded settings.
Wastewater data shows norovirus levels remain high nationwide, though not increasing. This season’s case counts are lower than last year’s unusually severe surge, but outbreaks continue to occur.
Health specialists say the best defense against these viruses remains testing when appropriate, vaccination for flu and Covid where recommended, and staying home when ill to prevent further spread.