Flu season might be winding down — but don’t stash the tissues just yet.
A little-known respiratory virus with no vaccine or treatment has been quietly picking up steam since the start of winter, helping drive a wave of illnesses across the country.
Wastewater surveillance, which tracks pathogens in sewage to measure community spread, shows that levels have reached the “high” category nationwide as of early March.
And yet, experts say most Americans probably haven’t heard of the virus, which causes symptoms that closely mimic other respiratory illnesses, like the common cold, flu or RSV.
“They’re definitely less familiar with it,” Dr. Sharon Nachman, chief of pediatric infectious diseases at Stony Brook Children’s Hospital, told The Post.
“When I hear someone say, ‘Oh my god, it’s March or April and I have the flu,’ my answer usually is, you may look like you have the flu, you may act like you have the flu, but you have human metapneumovirus (HMPV).”
Here’s everything you need to know about the virus making Americans cough, sneeze and sniffle their way into spring.
What is HMPV?
HMPV was first identified by researchers in the Netherlands in 2001, though studies suggest it had been circulating in humans for at least a half century prior.
Like the flu, it’s seasonal. Cases typically rise in January, peak in March and April, then drop as the weather warms in May.
“This is the right time of year for us to be seeing it,” Nachman said. “When flu season wanes, there’s a biologic niche that needs to be filled, and this respiratory virus jumps right in to do it.”
What are the symptoms of HMPV?
Most cases are mild and resolve within two to five days. Common symptoms include cough, fever, nasal congestion, sore throat, wheezing, shortness of breath and occasionally a rash.
In some cases, the illness can progress to pneumonia, bronchitis or middle ear infections. HMPV can also trigger asthma flare-ups or worsen chronic conditions such as COPD.
Severe illness is most likely during a person’s first HMPV infection, which puts young children at higher risk. Older adults and people with weakened immune systems are also more vulnerable to complications from the virus.
How common is HMPV?
Studies suggest that nearly everyone will catch at least one strain of HMPV over their lifetime, with most infections occurring before age 5. In children, the virus accounts for up to 12% of respiratory infections.
But despite its prevalence, tracking HMPV can be challenging.
“HMPV is rarely tested for when patients come in with a severe cold, so wastewater surveillance is one of the only ways to see how it’s spreading in the community,” said Dr. Alexandria Boehm, a professor of civil and environmental engineering at Stanford University and WastewaterSCAN principal investigator.
When someone is infected, they shed HMPV biomarkers — specifically nucleic acids — through their saliva, mucus, urine and feces.
“We can easily detect these in wastewater in areas where infections are present,” Boehm explained.
Recent data from WastewaterSCAN show viral activity nationwide has risen 70% since the beginning of February.
“Currently, levels of HMPV in wastewater are similar to this time last year, which mirrors what we are seeing at WastewaterSCAN sites in New York,” Boehm said.
How does HMPV spread?
HMPV spreads through direct contact with an infected person or by touching contaminated surfaces.
The virus is most contagious during the first few days of illness and generally remains contagious for one to two weeks. Symptoms typically appear three to seven days after exposure, according to the Cleveland Clinic.
How is HMPV diagnosed and treated?
Doctors usually diagnose HMPV based on symptoms, though a nasal or throat swab can confirm the infection in a lab.
There is no vaccine to prevent it, and no specific treatment for those who become infected.
That, Nachman suggested, helps explain why the virus remains relatively unfamiliar to the public.
“There’s not really a rush to diagnose it, because all I’m going to say is that you have a viral illness, go home, get some rest, and have some chicken soup and tea with honey,” she quipped.
“These are things that work for all viruses,” Nachman added. “Staying hydrated and taking care of yourself will always get you better faster.”
To reduce the risk of spreading HMPV, the CDC recommends staying home when sick, washing your hands regularly, and keeping commonly touched surfaces clean.
