HMPV: What You Need to Know

Human metapneumovirus (HMPV) is a very common respiratory virus that also infects any age individual. HMPV has been identified in the genus Pneumoviridae for the first time in 2001, which is very close to respiratory syncytial virus (RSV) and so on. While predominantly characterized by a low result on a symptom scale, a pathogenic lethal form is also present in an infant, an aged patient, or an immunocompromised patient.

The present article concerns HMPV, the homology between HMPV and RSV, HMPV vaccines currently available, and HMPV transmissibility.

HMPV vs. RSV: How Do They Compare?

However, respiratory viruses, such as HMPV and RSV, are distinct and characterized by a unique signature.

Similarities: 

• Transmission: Measles and coronavirus are all spread via respiratory secretions, by direct contact with contaminated surfaces or by close interpersonal contact.
• Symptoms: HMPV and RSV can cause similar symptoms, such as:

1. Cough
2. Runny nose
3. Fever
4. Shortness of breath

• Vulnerable Groups: Newborns, elderly patients and immunodeficient patients are most vulnerable.

Differences: 

• Seasonality: RSV infections are seasonal and RSV infections and HMPV infections are also prevalent in late fall and winter and late winter and spring respectively.
• Severity: RSV is the usual etiological agent for pathogenic lower respiratory tract infections such as bronchiolitis and pneumonia among neonates.
• Diagnosis: Although both may be diseaseable by molecular testing, they are genetically different.

Monitoring of these inequalities is of interest for the correct diagnosis and treatment, especially in the respiratory viral season.

HMPV Vaccine: Is One Available?

The development of the MPV vaccine has caught the attention of researchers, as its public health implications are accompanied by an outbreak of the virus.

Current Status: 

At present, no HMPV vaccine has been approved. Yet, conclusions obtained from research and clinical trials have consistently shown good results. Several candidate pediatric and geriatric vaccines are under development at present.

Challenges in Vaccine Development: 

Complexity of the Virus: HMPV is genomically diverse and vaccine target selection from a diverse population of naturally circulating strains is difficult.

Target Populations: Vaccines should be efficacious in a wide range of age (and beyond the very frail).

Hope for the Future: 

At the moment researchers are investigating novel applications e.g., mRNA vaccine technology in which the effectiveness has already been ascertained to be relevant to the treatment of other respiratory pathogens (e.g., COVID-19).

There [has been] no need to take infection control measures but through the use of good hygiene practices and avoiding contact with infected individuals until then, it is still effective.

Is Human Metapneumovirus Contagious?

No, HMPV is a highly transmissible virus and can be transmitted directly from person to person. The virus is most commonly transmitted through:

• Respiratory Droplets: Excretion (brisk cough, sneezing, speech, etc) may lead to the aerosolization of infective particles.
• Surface Contact: Any contact with contaminated surfaces and, therefore, contamination of the face will lead to infection.
• Close Contact: Socialization through physical hugs, kissing and handshakes with an infected person must be prevented so that the former can be infected through contamination.

Preventive Measures:

• Regularly wash hands with soap and water for a minimum of 20s.
• Avoid touching the face (especially the eyes, nose and mouth).

• Clean high-touch surfaces frequently, i.e., doorknobs, cell phones, counters, etc.
• Respirate during respiratory protection by covering mouth and nose with tissue or elbow during cough or sneeze.

Even just by observing the children’s behavior alone, it is possible to reduce the risk of infection by HMPV or the transmission of HMPV.

How Long Is Human Metapneumovirus Contagious?

The range of infectiousness of HMPV has variable duration depending on the infected individual, the infectiousness of infection, etc.

General Contagious Period: 

• Patients are usually infectious 2-8 days after virus exposure.
• The infectious period can start from 1-2 days before symptom onset and finish when symptoms resolve.

Factors Affecting Contagion Duration:

• Age: The virus may be exhaled for a longer duration by infants and the elderly.
• Immune Status: Immunocompromised individuals can remain contagious for several weeks.
• The severity of Symptoms: The severe symptom infected patient, who exhibits the highest virulence, could be more efficient in viral dissemination.

Returning to Normal Activities:

• During the self-isolation period, it is chosen not to reduce the interaction with the external world but to encourage social interactions (until the symptomatic patient has the latest AF  24 h and has not taken antipyretics).
• Additional precautions will have to be taken by health, daycare and preschool (HDCs) staff.

Diagnosis of HMPV contagion timeline is useful for its spread prevention and the protection of susceptible individuals.

Conclusion

Human Metapneumovirus is a common, but often undetected, respiratory virus that may lead to serious illness in some patient populations (2). Despite being very similar to RSV from almost all points of view, there are, of course, some aspects that deserve special attention.

Although (at this moment, the vaccine against HMPV is not on the market, research is going on to predict the preventative efficacy of the HMPV vaccine in the coming future. During the time before that, the best protection against that virus is by adhering to good hygiene and being cognizant of contagious periods.

Catching up with the data and preventative measures can defend the individual and the community from HMPV and other respiratory viruses.