Reports of an increase in respiratory virus cases in China have evoked dark echoes of the start of the Covid-19 pandemic almost exactly five years ago.
But despite the superficial similarities, this condition is very different and far less alarming, medical experts say.
The Chinese cases are being reported as infections with human metapneumovirus, known to doctors as HMPV. Here’s what we know so far:
What is HMPV?
It is one of the many pathogens that circulate around the world every year, causing respiratory diseases. HMPV is common — so common that most people will be infected while still children and may have several infections in their lifetime. In countries with cold weather months, HMPV can have an annual season, like the flu, while in places closer to the equator it circulates at lower levels year-round.
HMPV is similar to a virus better known in the United States — respiratory syncytial virus, or RSV. It causes symptoms similar to those associated with the flu and Covid, including cough, fever, nasal congestion and wheezing.
Most HMPV infections are mild, resembling bouts of the common cold. However, severe cases can lead to bronchitis or pneumonia, especially among infants, the elderly, and immunocompromised individuals. Patients with pre-existing lung conditions, such as asthma, chronic obstructive pulmonary disease or emphysema, are at higher risk of serious outcomes.
In higher-income countries, the virus is rarely fatal. In lower-income countries with weak health systems and poor surveillance, deaths are more common.
How long has this virus been around?
The virus was identified in 2001, but researchers say it has been circulating in humans for at least 60 years. While it’s not new, it doesn’t have the name recognition of influenza, Covid or even RSV, said Dr. Leigh Howard, associate professor of pediatric infectious disease at Vanderbilt University Medical Center.
One reason is that it is rarely discussed by name, except when people with a confirmed case are hospitalized.
“The clinical features are really hard to distinguish from other viral diseases and we don’t routinely test for HMPV like we do for Covid, influenza or RSV,” Dr Howard said. “So most infections go unrecognized and look like whatever respiratory thing is going on.”
How does a person become infected with HMPV?
The virus is spread mainly through droplets or aerosols from coughing or sneezing, through direct contact with an infected person or through exposure to contaminated surfaces – basically the same way people get colds, flu and Covid.
Is there a vaccine? Or a cure?
There is no vaccine against HMPV. But there is a vaccine for RSV, and research is underway to find a vaccination that could protect against both viruses with one vaccine, since they are similar. There is no antiviral treatment specific to HMPV. Treatment focuses on managing symptoms.
What does China say about this?
Chinese authorities have acknowledged that HMPV cases are on the rise, but have stressed that the virus is a known entity and not a major concern. The coronavirus that causes Covid-19 was a new pathogen, so people’s immune systems had not built up defenses against it.
At a press conference held by China’s Centers for Disease Control and Prevention on Dec. 27, Kan Biao, director of the center’s Institute of Infectious Diseases, said that HMPV cases are increasing in children 14 years old and younger. The increase was particularly noticeable in northern China, he said. Flu cases have also increased, he said.
Cases could increase during the Lunar New Year holiday in late January, when many people travel and gather in large groups, he said.
But overall, said Mr. Kan, “judging from the current situation, the scale and intensity of the spread of infectious respiratory diseases this year will be lower than last year.”
Official Chinese data shows that HMPV cases have been increasing since mid-December, both in outpatients and in emergency rooms, according to Xinhua, the state-run news agency. Some parents and social media users were unfamiliar with the virus and sought advice online, the agency said. he urged calm and the usual precautions, such as frequent hand washing and avoiding crowded places.
At a regular media briefing on Friday, a State Department spokesman reiterated that cases of flu and other respiratory viruses have been steadily increasing this time of year but that they “appear to be less severe and spread on a smaller scale than last year.”
Chinese officials said last week they would set up a surveillance system for pneumonia of unknown origin. It will include procedures for laboratories to report cases and for disease control and prevention agencies to verify and handle them, state broadcaster CCTV said.
What was the public response in China?
Online, amid comments from people who said they had never heard of HMPV and expressed concern that it was a new pathogen, state media tried to reassure people, warning them not to blindly take antiviral drugs.
Some users have joked that they might finally run out of the masks they stockpiled during the coronavirus pandemic. Many commentators have discussed a general increase in the disease, not just HMPV: “Why does the flu hurt so much” was trending on Weibo, a social networking platform, on Monday.
What does the World Health Organization say?
The WHO has not expressed concern. Dr. Margaret Harris, a spokeswoman for the organization, cited weekly reports from Chinese authorities that showed a predictable rise in cases.
“As expected for this time of year, in the Northern Hemisphere winter, there is a month-to-month increase in acute respiratory infections, including seasonal influenza, RSV and human metapneumovirus,” he said via email.
On Tuesday, the agency issued a statement saying, “WHO is in contact with Chinese health officials and has not received any reports of unusual outbreak patterns.” He added, “Chinese authorities report that the health care system has not been overwhelmed and there have been no emergency declarations or responses.”
Should I be worried?
The reports coming out of China are reminiscent of those from the early, confusing days of the Covid pandemic, and the WHO is still urging China to share more information about the origins of this outbreak, five years on.
But the current situation is different in key respects. Covid was a virus that was transmitted to humans from animals and was previously unknown. HMPV has been well studied and there is extensive testing capacity for it. There is widespread population-level immunity to this virus worldwide. there was none, for Covid. A severe bout of HMPV can strain hospital capacity—especially pediatric wards—but it does not overwhelm medical centers.
“However, it is also vital for China to share its data on this outbreak in a timely manner,” said Dr Sanjaya Senanayake, an infectious disease expert and associate professor of medicine at the Australian National University. “This includes epidemiological data about who is getting infected. We will also need genomic data to confirm that HMPV is the culprit and that there are no major mutations of concern.”
Vivian Wang contributed reporting from Beijing.
