Understanding Human Metapneumovirus—Risks and Prevention

The human metapneumovirus poses little threat to the general population, typically causing only mild symptoms similar to those of the common cold.

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In the wake of the COVID-19 pandemic, the human metapneumovirus (HMPV), currently spreading in China, has drawn significant attention. In the “Health 1+1” program, Xiaoxu Sean Lin, a U.S. virology expert and former director of a virology laboratory at the U.S. Army Research Institute, discussed the characteristics and symptoms of HMPV infection and shared effective prevention strategies.

HMPV was first discovered by scientists from the Netherlands in 2001, but it had already existed for at least 50 years. Since it typically causes only mild symptoms, it often goes undetected.

Recently, articles have suggested that the mortality rate of HMPV infection is as high as 43 percent. However, Lin said that this figure is misleading. If the mortality rate were truly close to 50 percent, HMPV would have already become a major global concern, similar to Ebola or COVID-19.

A study conducted in the United States found that among patients who had undergone hematopoietic cell transplantation, the mortality rate for HMPV infection could reach 43 percent. However, this finding applies only to those with severely weakened immune systems and does not represent the general population.

Common symptoms of HMPV infection include:

• Runny nose
• Cough
• Shortness of breath
• Sore throat
• Wheezing
• Fever
• Rash

HMPV primarily infects the upper respiratory tract, but in some cases, it can also spread to the lower respiratory tract, Lin said. This progression is closely related to the immune status of the affected person. If the immune system is weakened, the virus is more likely to bypass the upper respiratory tract and infect the lower respiratory tract, potentially leading to conditions such as bronchitis, pneumonia, and other inflammatory responses.

After infecting the bronchial epithelium, HMPV can cause edema and inflammation in the fluid-filled tissue and space surrounding the air sacs in the lungs.

In rare cases, HMPV infection can lead to severe complications, such as encephalitis (inflammation of the brain) and diffuse alveolar hemorrhage (bleeding in the lungs’ air sacs).

HMPV primarily targets dendritic cells, airway epithelial cells, and alveolar macrophages, Lin said. These cells possess surface receptors facilitating viral entry, making them particularly vulnerable to infection.

Populations More Susceptible to Infection

In most cases, HMPV infections in adults cause mild symptoms, and recovery typically occurs within two weeks, Lin said. However, the infection can lead to more severe symptoms in people with weakened immune systems. Patients who are infected should avoid contact with children or those with compromised immunity.

Populations more susceptible to HMPV infection include:

• Those with weakened immune systems, such as cancer patients, individuals undergoing chemotherapy, and organ transplant recipients
• Those with chronic underlying conditions, such as hypertension (high blood pressure), diabetes, chronic liver disease, or kidney disease
• Those experiencing complications or side effects after vaccination
• Those who have had multiple COVID-19 infections and have not fully recovered
• Children younger than 5 and adults older than 65
• Those with chronic bronchitis, chronic obstructive pulmonary disease, or lung damage caused by long-term smoking

No Effective Medications Available

Currently, there are no medications available to treat HMPV, Lin said. In fact, many infectious diseases lack specific treatments. For example, while antiretroviral drugs are available for HIV, they cannot cure the disease. Even for COVID-19, despite substantial global investment, antiviral medications are only moderately effective during the early stages of infection and cannot fully suppress the virus.

HMPV has not been a major focus of research because infections are typically mild, and no targeted treatments have been developed. Current treatment strategies primarily involve the use of antihistamines to reduce inflammation, along with measures to manage symptoms such as fever. Supportive therapies, including techniques to improve breathing, can also help the body fight off the virus on its own.

Modes of Transmission and Prevention

HMPV is most likely to spread from an infected person to others through the following routes, according to the Centers for Disease Control and Prevention:

• Secretions produced by coughing or sneezing
• Close personal contact, such as touching or shaking hands
• Touching the mouth, nose, or eyes after coming into contact with objects or surfaces contaminated with the virus

To prevent HMPV infection, Lin recommended reinforcing routine respiratory disease prevention measures. These include frequent handwashing, ensuring good indoor ventilation, and avoiding crowded places with poor air circulation. Strengthening the immune system is also essential, achieved through a balanced diet, regular exercise, sufficient sleep, stress management, and refraining from smoking.

Additionally, Lin emphasized the importance of proper ventilation and breathing fresh air.

“Spending time in nature and breathing fresh air can make people feel rejuvenated and full of energy, right?” he said. “So, it is not necessary to wear a mask all the time.”

Lack of Transparency in Beijing’s Reporting

Although a high number of HMPV infections have been reported in China, Lin said that for now, HMPV is unlikely to trigger the next major pandemic. He pointed out that the United States also experienced a minor surge in HMPV infections last year, but it neither led to a global pandemic nor posed a significant increase in pathogenic threats. Furthermore, there have been no reports this year from other countries indicating that HMPV has developed new lethal mutations or significantly enhanced transmissibility.

Lin also highlighted the Chinese regime’s lack of transparency in releasing information, which makes it difficult to assess the actual situation. It remains unclear whether patients infected with HMPV are also co-infected with other viruses, further complicating efforts to determine whether HMPV is the primary cause of the recent surge in severe respiratory cases in China. Viruses such as the one that causes COVID-19, respiratory syncytial virus, and influenza may also be contributing factors, Lin said.

The worsening political and economic situation in mainland China has also placed significant stress on people’s daily lives, Lin said.

“Excessive mental stress can lead to a severe decline in immune system function,” he said. “In many cases, the mind gives way before the body. I find it especially unfortunate for those who succumb to this.

“I believe it is essential to strengthen one’s resilience from a mental and spiritual perspective. Focusing on spiritual growth can be tremendously helpful in facing potential challenges and crises in the future.”