It has certainly not escaped your attention that a new wave of respiratory infections in northern China is taking place, due to human metapneumovirus (HMPV) infections. A health situation which inevitably takes us back to the period of COVID-19, a pandemic that we will not soon forget. However, the two health situations are very distinct, and the World Health Organization (WHO) is rather reassuring about the current facts.
Even though it is part of the list of pathogens known as priority (available here), she classified it as being low to medium risk. For the moment, it therefore does not constitute a real threat likely to cause a public health emergency of international concern (PHEIC), that is to say a global health crisis.
Molecular structure and transmission dynamics of HMPV
The human metapneumovirus, identified in 2001, belongs to the family of Pneumoviridaea group of respiratory viruses whose genomic structure deserves special attention. Its genome, made up of single-stranded RNA of negative polarity, requires transcription into messenger RNA before any protein synthesis – a mechanism which directly influences its replication capacity in host cells.
So that the infected cell can “read” and use this plan to make new viruses, it must first be “turned around” so that it is in the right direction. It’s a bit like trying to build something with instructions written backwards: you first have to copy them the right way up before you can begin. This process therefore slightly slows down its replication.
Transmission mechanisms, mainly by respiratory aerosols, involve viral particles between 5 and 10 micrometers in size. These droplets, carrying viral material, can remain suspended in the air for several hours, particularly in closed and poorly ventilated environments. The HMPV is transmitted mainly through the air, when we cough or sneeze.
HMPV: an enemy of the respiratory tract
HMPV is a virus that particularly affects the cells that line our respiratory tract, such as the nose and lungs. To understand how it works, imagine the virus as a key searching for its lock: it has special proteins on its surface (the F and G glycoproteins) which allow it to attach to and penetrate respiratory cells. It is for this reason that the symptoms mainly manifest themselves in the nose, throat and lungs.
Just like COVID-19, some people are more susceptible to this virus than others. Young children under the age of two are particularly vulnerable, because their immune defense system is still under construction – like an army that does not yet have all its soldiers (lymphocytes) well trained.
Likewise, people whose immune defenses are weakened, whether due to cancer treatment, a transplant or HIV, are more likely to develop serious forms of the disease, because their protection system is less effective. « The youngest and oldest are most at risk, as well as immunocompromised people, that is to say those whose immune system is weakened. » explains Dr. Harris in this WHO publication about HMPV.
Lessons from COVID-19 to limit the spread of HMPV
The COVID-19 period has provided us with essential experience to better manage HMPV, particularly in three key areas. First, virological surveillance systems, significantly strengthened during the pandemic, now allow earlier detection of respiratory pathogens. Real-time analysis of viral sequences, initially developed for SARS-CoV-2, is now being applied to HMPV, facilitating the monitoring of mutations and the assessment of epidemic risks.
Secondly, the understanding of air transmission mechanisms, deepened during the COVID-19 crisis, directly influences HMPV prevention strategies. Ventilation protocols, mask wearing and physical distancing, scientifically validated against SARS-CoV-2, show comparable effectiveness against HMPV.
Finally, the global research infrastructure, mobilized during the pandemic (with more than 240 daily publications on COVID-19), today maintains strong vigilance on emerging respiratory viruses. This continuity of research, essential in the face of the thousand weekly deaths still attributed to COVID-19, will directly benefit the understanding and management of HMPV.
For now, There is therefore no point in panicking.. « Levels of respiratory infections reported in China are within the usual range for the winter season » explains the WHO. According to data communicated by Beijing to the institution, the pressure on hospitals is less compared to last year at the same period. No emergency measures have therefore been put in place. The virus that worries the Chinese authorities the most is a much better known one: the flu, which is on the rise.
- A wave of human metapneumovirus (HMPV) infections in China remains under control, without posing an immediate global threat.
- HMPV primarily targets the respiratory tract and affects vulnerable populations such as children and the immunocompromised.
- Lessons learned from COVID-19, particularly on surveillance and prevention, will make it possible to better manage the spread of this virus.
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