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Five years after COVID-19 began spreading in the Chinese city of Wuhan, cases of human metapneumovirus, which also causes respiratory infections, have risen in the country, particularly among children.
Between December 23 and 29, 2024, cases of HMPV rose from the week before, particularly in Northern China and in children under 14, the Chinese Center for Disease Control and Prevention said on January 2. Cases of influenza, rhinovirus, and mycoplasma pneumoniae also increased, it said.
Videos of crowded hospitals in China posted online are reminiscent of the early days of the COVID-19 pandemic, and Google searches in the US related to HMPV and the likelihood a pandemic and lockdowns are on the horizon have spiked in recent days.
But HMPV doesn't pose a similar threat to COVID because it is not a new virus, meaning we understand how it affects humans and most people already have some immunity against it.
HMPV usually causes cold-like symptoms such as coughing, wheezing, a runny nose, and a sore throat that clear on their own in between three to six days. But it can lead to more serious conditions such as bronchitis or pneumonia, particularly in young children, adults over 65, and people who are immunocompromized. Infections are most common in colder seasons.
Most people get HMPV before they turn five, meaning symptoms tend to be more severe in children as they haven't yet built up immunity against it. A person gains some immunity to the virus when they first catch it, so symptoms are typically mild if they are re-infected.
It spreads through coughing and sneezing, direct contact with an infected person, or from touching surfaces contaminated with the virus, such as phones.
There are no existing antiviral medications for HMPV, but if a patient becomes seriously ill, doctors may use oxygen therapy to help them breathe or antibiotics to treat secondary infections. There isn't a vaccine, but there are some in development.
HMPV was first identified in the Netherlands in 2001, but is believed to have been infecting humans for decades.
"This is very different to the COVID-19 pandemic," professor Jill Carr, a virologist at the College of Medicine and Public Health at Flinders University, Australia, said.
"The virus was completely new in humans and arose from a spill-over from animals and spread to pandemic levels because there was no prior exposure or protective immunity in the community," Carr said of COVID-19.
There is a broad understanding of how HMPV spreads and affects humans, and diagnostic tests to identify it.
"HMPV can certainly make people very sick, and high case numbers are a threat to effective hospital services, but the current situation in China with high HMPV cases is very different to the threats initially posed by SARS-CoV-2 resulting in the COVID-19 pandemic," Carr said.
A spokesperson for the World Health Organization told Business Insider via email that higher levels of respiratory illnesses, including HMPV, are expected at this time of year, adding that the rate of "influenza activity" is lower than the same period last year.
On January 2, the Chinese CDC advised people to take health precautions, such as maintaining good hygiene, covering their mouths and noses with a tissue or elbow when coughing or sneezing, washing their hands frequently with soap and water for at least 20 seconds, and wearing masks in crowded spaces.
But in a press conference on Friday, the Chinese government also appeared to push back against online speculation that the situation could overhwlem hospitals and lead to a new pandemic, The Guardian reported.
"Respiratory infections tend to peak during the winter season," Chinese foreign ministry spokesperson Mao Ning said on Friday. "The diseases appear to be less severe and spread with a smaller scale compared to the previous year."
Vasso Apostolopoulos, a professor of immunology at the School of Health and Biomedical Sciences, RMIT University, Australia, said that the growing number of cases and pressure on healthcare systems in densely populated regions like China highlights the need for enhanced surveillance strategies.
"Ensuring effective monitoring and timely responses will be key to mitigating the public health risks of this outbreak," she said.
