Studies of a surge in circumstances of a respiratory virus in China have evoked darkish echoes of the beginning of the Covid-19 pandemic virtually precisely 5 years in the past.

However regardless of the floor similarities, this case could be very completely different, and much much less worrisome, medical consultants say.

The Chinese language circumstances are reported to be infections with human metapneumovirus, identified to medical doctors as HMPV. Here’s what we all know up to now:

What’s HMPV?

It’s considered one of a number of pathogens that flow into internationally annually, inflicting respiratory sicknesses. HMPV is frequent — so frequent that most individuals shall be contaminated whereas they’re nonetheless kids and will expertise a number of infections of their lifetimes. In international locations with months of chilly climate HMPV can have an annual season, very similar to the flu, whereas in locations nearer to the Equator it circulates at decrease ranges all 12 months lengthy.

HMPV is much like a virus that’s higher identified in the US — respiratory syncytial virus, or R.S.V. It causes signs very similar to these related to flu and Covid, together with cough, fever, nasal congestion and wheezing.

Most HMPV infections are gentle, resembling bouts of the frequent chilly. However extreme circumstances can lead to bronchitis or pneumonia, significantly amongst infants, older adults and immunocompromised individuals. Sufferers with pre-existing lung situations, reminiscent of bronchial asthma, continual obstructive pulmonary illness or emphysema, are at increased danger of extreme outcomes.

In higher-income international locations, the virus is never deadly; in lower-income international locations, with weak well being programs and poor surveillance, deaths are extra frequent.

How lengthy has this virus been round?

The virus was recognized in 2001, however researchers say it has circulated in people for a minimum of 60 years. Although it’s not new, it doesn’t have the identify recognition of influenza, Covid and even R.S.V., mentioned Dr. Leigh Howard, an affiliate professor of pediatric infectious illness at Vanderbilt College Medical Heart.

One purpose is that it’s hardly ever mentioned by identify, besides when individuals are hospitalized with a confirmed case of it.

“The scientific options are actually troublesome to differentiate from different viral sicknesses, and we don’t routinely check for HMPV the best way we do for Covid, flu or R.S.V.,” Dr. Howard mentioned. “So most infections go unrecognized and are chalked as much as no matter respiratory factor goes round.”

How does an individual get contaminated with HMPV?

The virus spreads primarily by means of droplets or aerosols from coughing or sneezing, by means of direct contact with an contaminated particular person or by means of publicity to contaminated surfaces — mainly the identical methods individuals get colds, flu and Covid.

Is there a vaccine? Or a remedy?

There is no such thing as a vaccine in opposition to HMPV. However there’s a vaccine for R.S.V., and analysis is underway to discover a vaccination that might defend in opposition to each viruses with one shot, since they’re comparable. There is no such thing as a antiviral remedy particularly for HMPV; remedy focuses on administration of signs.

What’s China saying about it?

The Chinese language authorities have acknowledged that HMPV circumstances are rising, however have emphasised that the virus is a identified entity and isn’t a significant concern. The coronavirus that causes Covid-19 was a brand new pathogen, so individuals’s immune programs had not constructed up defenses in opposition to it.

At a information convention held by China’s Heart for Illness Management and Prevention on Dec. 27, Kan Biao, the director of the middle’s Institute for Infectious Ailments, mentioned that HMPV circumstances had been rising amongst kids 14 years and youthful. The rise was particularly notable in northern China, he mentioned. Influenza circumstances have additionally elevated, he mentioned.

Instances might spike throughout the Lunar New Yr vacation, on the finish of January, when many individuals journey and collect in massive teams, he mentioned.

However total, Mr. Kan mentioned, “judging from the present scenario, the size and depth of the unfold of respiratory infectious ailments this 12 months shall be decrease than final 12 months’s.”

Official Chinese language information reveals that HMPV circumstances have been rising since mid-December, in each outpatient and emergency circumstances, in response to Xinhua, the state information company. Some mother and father and social media customers had been unfamiliar with the virus and had been searching for recommendation on-line, the outlet mentioned; it urged calm and peculiar precautions reminiscent of washing one’s palms ceaselessly and avoiding crowded locations.

In a routine media briefing on Friday, a spokesperson for the Overseas Ministry reiterated that circumstances of influenza and different respiratory viruses routinely enhance presently of 12 months however that they “seem like much less extreme and unfold on a smaller scale in contrast with the earlier 12 months.”

Chinese language officers mentioned final week that it could arrange a monitoring system for pneumonia of unknown origin. It’s going to embody procedures for laboratories to report circumstances and for illness management and prevention businesses to confirm and deal with them, the state broadcaster CCTV reported.

What has the general public response in China been?

On-line, amid feedback from individuals saying that they had by no means heard of HMPV and expressing concern that it was a brand new pathogen, state media shops have sought to reassure individuals, warning them in opposition to blindly taking antiviral drugs.

Some customers have cracked jokes, saying that they may lastly burn up the masks that they had stockpiled throughout the coronavirus pandemic. Many commenters have mentioned a common uptick in sickness, not simply HMPV: “Why does the flu harm a lot” was trending on Weibo, a social media platform, on Monday.

What does the World Well being Group say?

The W.H.O. has not expressed concern. Dr. Margaret Harris, a spokeswoman for the group, cited weekly reviews from the Chinese language authorities that confirmed a predictable rise in circumstances.

“As anticipated for this time of 12 months, the Northern Hemisphere winter, there’s a month-over-month enhance of acute respiratory infections, together with seasonal influenza, R.S.V. and human metapneumovirus,” she mentioned by e-mail.

Ought to I fear?

The reviews coming from China are evocative of these from the primary, complicated days of the Covid pandemic, and the W.H.O. continues to be urging China to share extra details about the origin of that outbreak, 5 years on.

However the present scenario is completely different in key respects. Covid was a virus that spilled over into people from animals and was beforehand unknown. HMPV is properly studied, and there’s widespread capability to check for it. There may be broad population-level immunity to this virus globally; there was none, for Covid. A extreme HMPV season can pressure hospital capability — significantly pediatric wards — however doesn’t overwhelm medical facilities.

“Nevertheless, it’s also important for China to share its information on this outbreak in a well timed method,” mentioned Dr. Sanjaya Senanayake, a specialist in infectious ailments and affiliate professor of drugs on the Australian Nationwide College. “This contains epidemiologic information about who’s getting contaminated. Additionally, we’ll want genomic information confirming that HMPV is the offender, and that there aren’t any important mutations of concern.”

Vivian Wang contributed reporting from Beijing.