The virus fueling pandemic fears in China has infected thousands of Americans in the past year, according to federal data. 

Weekly CDC data indicates that almost 28,000 Americans have contracted human metapneumovirus (HPMV) since January 2024. This respiratory illness, previously unfamiliar to many, has been described as ‘the most important virus you’ve never heard of.’

The number of infections saw a notable increase in April 2024, with a particular week recording 1,666 positive test results at its peak. This figure represented eight percent of all tests conducted during that specific week.

The latest CDC data for the week ending December 28 shows there were 260 positive tests, a two percent positivity rate. 

On average, since Thanksgiving, 200 to 350 positive cases have been reported in the US every week, a number health officials say is not unusual.

Known for typically causing symptoms akin to a cold, HMPV has been linked to a viral outbreak in China. Reports indicate that this outbreak has placed significant strain on hospitals located in the northern provinces of the country.

While the virus has sparked pandemic fears, rates of other winter illnesses like Covid and respiratory syncytial virus (RSV) have remained significantly higher. 

For comparison, over 1million Americans have visited the emergency room for RSV, and nearly 10million have been struck with influenza since October.

Nearly 28,000 Americans have been sickened with respiratory illness HMPV since this time last year, the CDC estimates. The surge in HMPV and other respiratory illnesses has led some states to bring back masking rules (stock image)

HMPV first emerged in 2001 and typically causes symptoms of a common cold like cough, fever, and runny nose.

But more severe symptoms such as bronchitis, bronchiolitis and pneumonia can occur, with sufferers experiencing a shortness of breath, severe cough or wheezing. 

Because the virus is usually mild, its exact death rate is unknown. But experts estimate anywhere from 10 to 30 percent of patients hospitalized with HMPV die in the US.

Roughly 20,000 US children under age five are hospitalized with HMPV every year.  

Similar to Covid, HMPV spreads through respiratory droplets that circulate in the air when a person coughs or sneezes. 

Close personal contact like shaking hands and touching contaminated surfaces can also spread the disease. 

There are no vaccines or specific treatments for HMPV. 

According to the latest CDC data available, from the week of December 28, HMPV had a test positivity rate of 1.9 percent. 

Out of about 13,800 total tests for that week, that adds up to just under 300 confirmed cases. 

The test positivity rate for the week of November 30 was 0.9, half that of the month after. 

And at this time last year, the CDC recorded a 1.2 percent test positivity rate.    

According to CDC regional data, also from December 28, midwestern states Missouri, Kansas, Nebraska, and Iowa had triple the rates of the US on average. These states make up Region 7. 

MIDWEST SURGE: Region 7, which covers Missouri, Kansas, Nebraska and Iowa, is seeing sky-high rates of HMPV compared to the rest of the country

This map shows how the CDC breaks down different regions of the US for its weekly breakdown of respiratory infections

Regions 1 and 2 had the lowest test positivity rates at 0.9 percent. These areas include northeastern states like Maine, New York, Massachusetts, Connecticut, and New Jersey. 

Region 1 conducted 2,270 tests while Region 2 conducted 1,855. 

While HMPV cases are increasing, other respiratory illnesses and influenza have seen more significant spikes. 

China is also seeing spikes in flu cases, with one in three tests coming back positive. This adds up to just under 7,000 new cases from December 29 until January 5.

However, China’s CDC said Thursday the flu is showing signs of slowing while other respiratory illnesses continue to spike.

NORTHERN PROVINCES: The above graph shows the proportion of emergency room visits for influenza by year in the Northern provinces

SOUTHERN PROVINCES: The above graph shows the proportion of emergency room visits for influenza by year in the Southern Provinces

In the US, the flu and respiratory viruses are all on the rise. 

According to the CDC, the level of respiratory illness activity in the US is ‘high’ and it is ‘high’ or ‘very high’ in a majority of states.

The virus with the highest level is Covid-19. Flu and RSV are at ‘moderate levels.’ 

However, emergency department visits for flu and RSV are ‘very high’ and increasing, while visits are ‘low’ but increasing for Covid-19. 

The states with the highest levels of respiratory activity were Kansas, Oklahoma, Texas, Arizona, Utah, Louisiana, Tennessee, Kentucky, Georgia, and Florida.

Cases of the flu and RSV reached new highs this season, with 19 percent and 13 percent of samples testing positive for those viruses in the week ending December 28, respectively.

About seven percent of tests were positive for Covid.  

The CDC estimates there has been 1.2million doctors visits for RSV, 60,000 hospitalizations and 3,100 deaths between October 1, 2024 and December 14.

Experts have cautioned that HMPV, which produces flu-like symptoms, can lurk in the body for days and so it can be easily passed on to others

For Covid, estimates are 4.9million cases, 1.1million visits, 130,000 hospitalizations and 15,000 deaths.

And for the flu, estimates are 9.3million cases, 4.2million visits, 140,000 hospitalizations and 13,000 deaths in the same time period.  

For the week ending December 28 — the latest available — 1.2 percent of hospital visits were for the Covid, up from less than one percent a month prior. 

RSV accounted for one percent, up from 0.6 percent a month prior, and flu visits accounted for 5.2 percent of visits — a sharp increase from just one percent in the week ending November 30.

Hospitalizations are also up for all the respiratory viruses and they jumped to two percent for Covid and RSV and four percent for flu at the end of December.

Deaths edged up slightly, but made up less than one percent of overall death rates.