In recent days in China there is an increase in the number of infections from Human metapneumovirus (hMPV)a respiratory virus of the Pneumoviridae family isolated in 2001 by a team of researchers in the Netherlands. This is not a new viral strainbut of a rather common virus that has a global spread and seasonal distribution similar to most respiratory viruses. The infection generally causes mild symptoms similar to the common cold in healthy adults, but has more evident and sometimes more serious effects among children under 5 years old. It can also cause bronchial and pulmonary complications in the elderly and immunosuppressed subjects.
From what was reported by the World Health Organization (WHO), based on data published by China, in these weeks coinciding with the winter season, all respiratory infections are on the increasenot only due to hMPV, but also seasonal influenza, rhinoviruses and other influenza-like viruses. Furthermore, the flu illnesses reported in China in recent weeks fall within the range expected for the winter season.
What is the hMPV virus and how is it transmitted
hMPV is a single-stranded RNA virus belonging to the Metapneumovirus genus. It was first isolated in 2001 by a team of researchers in the Netherlands on a group of 28 children hospitalized. Subsequent studies also made it possible to establish that the viral strain had already been in circulation for about 50 years. It has an incubation cycle of 3 to 6 days and a variable duration of infection is estimated, but comparable to that of other respiratory viruses.
The spread of the hMPV virus is wider in winter periodis transmitted through the famous droplets respiratory, i.e. droplets of secretions dispersed into the air by infected people through sneezing or coughing or by contact with contaminated surfaces. The virus manages to penetrate inside the host cell thanks to the action of particular elements so-called viral fusion proteins (F), which are located on the external protective casing.
What are the symptoms and how are they treated?
The most common symptoms are those affecting the upper and lower respiratory tracts. The most frequent are fever, cough, wheezing, rhinorrheaasthma, bronchiolitis up to pneumonia in severe cases. Furthermore, it is possible that in the presence of hMPV they may occur co-infections with other pathogensboth viruses and bacteria. Most people have mild symptoms and recover within a few days.
Some cases especially among children, which they appear to be more exposed to contagion during the first 5 years of life and particularly under one year of age, may result in hospitalization for bronchitis, bronchiolitis or pneumonia.
To date no drugs are available antivirals or vaccines against hMPV: however, after 20 years of research, considerable progress has been made in the knowledge of this virus, its mechanism of infection and therefore it is expected that vaccines for the prophylaxis and therapy of this virus will soon be available. Among the main candidates for vaccine therapy there are two mRNA vaccines. For the moment, as also recommended by the World Health Organization, the best defense is prevention through adequate hygiene measuresnow already known and widespread since the COVID-19 pandemic: cover your nose and mouth if you sneeze or cough, wash your hands frequently and avoid going out if you have symptoms.
The situation in Italy regarding human Metapneumovirus infections
As regards the national situation based on the weekly bulletin RespiVirNet of the Istituto Superiore di Sanità relating to the week from 23 to 29 December 2024 the1.2% of the clinical samples analyzed tested positive for Metapneumovirus, while 16.8% tested positive for seasonal influenza strains.
There is therefore no reason to be alarmed, also because every year the RespiVirNet bulletins show a percentage of samples positive for the hMPV virus, however rather small.
