What is HMPV, the respiratory virus surging in China?

A flu-like viral disease has surged in China in recent months, particularly infecting children, raising concerns about its potential spread.

Cases of human metapneumovirus (HMPV) have also been reported from India amid seasonal winter patterns of a rise in respiratory illnesses. Chinese health officials are piloting a monitoring system while authorities in India have advised people not to panic.

Here is what to know about the virus, which transmits like other respiratory diseases such as flu and COVID-19.

What is HMPV?

Human metapneumovirus is a respiratory virus that causes flu or cold-like symptoms.

The virus peaks during late winter and spring, according to the United States-based Centers for Disease Control and Prevention.

First identified in 2001 in the Netherlands, the disease is very common, infecting almost every child by the age of five.

HMPV is tested by collecting a sample of mucus from the nose or throat using a swab. Similar to COVID, the sample is analysed in a lab, often with RT-PCR tests. Other methods, like antigen tests, can also identify the virus.

How is HMPV transmitted?

HMPV enters the body through the nose, mouth, or eyes, typically after inhaling droplets from an infected person coughing, sneezing, or breathing, or after touching contaminated surfaces.

These modes of transmission are similar to those of the common cold, flu, and other respiratory viruses.

What does HMPV do to the body?

After entering the body, the virus attaches to the epithelial cells lining the respiratory tract, which includes airways and the lungs.

These epithelial cells form a protective barrier in the airways, helping to guard the respiratory system while clearing mucus, dust, and other debris.

Once inside the cells, the virus replicates, producing more viral particles. These newly formed viruses infect neighbouring cells, spreading through the respiratory epithelium.

The body’s immune system detects the infection and launches an inflammatory response to combat the virus. While essential for clearing the virus, this reaction contributes to the symptoms of the infection, such as nasal congestion and a cough.

Pedestrians walk past a wall mural promoting awareness on using face masks in Bengaluru on January 6, 2025, amid concerns and alleged media reports stating that two cases of HMPV were detected in India’s Karnataka state. [Idrees Mohammed/AFP]

Which countries have seen a rise in HMPV cases?

In northern China, HMPV cases have been rising among children 14 years and younger, according to Kan Biao, director of China’s Institute for Infectious Diseases.

The spike coincides with the cold winter months, during which respiratory infections are more prevalent.

In response to the rise in cases, China’s National Disease Control and Prevention Administration said it is piloting a monitoring system for pneumonia of unknown origin.

Countries like India and the United Kingdom have also reported seasonal increases in HMPV since late 2024.

India has reported seven confirmed cases of HMPV across several states, including Karnataka, Gujarat, Maharashtra, and Tamil Nadu.

The Indian government has advised states to boost surveillance for respiratory illnesses and advised the public not to panic and maintain standard precautions such as regularly washing hands and avoiding close contact with others.

In the UK, between December 23 and 29 last year, some 4.5 percent of lab-tested samples were positive for HMPV, a slight increase from the previous week. In comparison, 29.5 percent were positive for influenza, and 2.5 percent for COVID-19.

Precise global data on the virus is scarce as surveillance and reporting of the virus is not as robust or routine as the flu or COVID-19.

Is it contagious or deadly? Who is more at risk?

HMPV spreads easily, but it is not typically deadly in healthy individuals.

Most people have mild symptoms resembling the common cold or flu and recover fully within seven to 10 days.

Accurate mortality rates have been difficult to measure owing to limited data and overlap with other respiratory illnesses. However, in low-resource settings where access to healthcare is limited, HMPV-linked deaths have been relatively more common.

Additionally, within some people, the virus can lead to more severe respiratory complications, such as bronchitis, inflammation of the airways leading to the lungs, or pneumonia, infection of the lung tissue. This includes high-risk groups such as infants, older adults, and immunocompromised individuals.

Infants, for example, have smaller and more delicate airways, which can become easily inflamed or blocked during respiratory infections. Moreover, their immune systems and bodies are still developing, making it harder to fight the virus.

Ageing also reduces the immune function, while underlying health conditions make it harder to get rid of the virus.

What are the symptoms of HMPV infection?

These symptoms typically appear within three to six days after being infected, and often include:

• Cough
• Fever
• Nasal congestion
• Wheezing
• Breathlessness
• Sore throat

Vulnerable groups may experience more severe and prolonged symptoms.

How can HMPV infection be treated?

There is no antiviral treatment or vaccine designed just for HMPV.

Instead, treatment focuses on managing symptoms, such as using fever medications, staying hydrated, and resting.

Severe cases, especially those involving pneumonia or significant respiratory distress, may require hospitalisation and supportive care like oxygen therapy.