After a peak in infections reached in January, the first months of 2024 saw the decline in the epidemic of pneumonia at Mycoplasma pneumoniae (Mp). Of unusual intensity, this wave started in November 2023, mainly affecting children and young adults. Although a stabilization of monitoring indicators was observed from February 2024, the levels remained higher than those in the years before Covid.
This resurgence, also observed in Europe and South-East Asia, could result from the conjunction of the lifting of Covid control measures and an epidemic cycle, suggests the High Authority for Health (HAS). The absence of acquired immunization after an infection and the circulation of different genotypes explain the occurrence of cyclical epidemic outbreaks. The previous wave in France dates from the 2010-2011 season.
Mp is a so-called atypical bacteria, strictly human, which is transmitted by fine droplets during close contact with symptomatic people after an incubation period of one to three weeks. The infection mainly affects a young population with a peak incidence observed between 4 and 15 years of age but can affect all age groups.
Most infections Mp are limited to upper respiratory problems with symptoms of the ENT sphere which resolve spontaneously. Lower respiratory infections can also be observed, Mp being the second agent, after pneumococcus, involved in acute community-acquired bacterial pneumonia.
Probabilistic antibiotic therapy with macrolides
In an “Urgent DGS” and rapid responses from the HAS, the authorities recalled that a diagnosis of pneumonia Mp should be considered in the presence of: acute community pneumonia with failure of antibiotic therapy with amoxicillin or amoxicillin-clavulanic acid within 48-72 hours; a picture of acute community pneumonia with progressive onset, sometimes accompanied by extra-respiratory signs. The existence of grouped cases is also evocative (communities, schools, family, army, etc.).
Generally, a progressive cough is observed, more or less associated with a febrile syndrome. The initial cough is dry and becomes productive over three to four weeks. The respiratory signs are discreet and there is little change in general condition. However, cases of asthma exacerbation have been reported in some children with wheezing on auscultation.
Extra-respiratory manifestations are present in almost a quarter of cases. Among the most common signs: myalgia, hepatic cytolysis or even maculopapular skin rashes. These are autoimmune manifestations and/or direct infectious lesions.
In case of strong clinical suspicion, probabilistic antibiotic therapy with macrolides (azithromycin or clarithromycin) must be started without waiting for the results of the chest x-ray, which is also indicated to support the diagnosis and look for complications. There may be a radiological delay of 72 hours from the start of symptoms. On the other hand, serology is useless for diagnosis in the acute phase.
The outcome under antibiotic therapy, particularly fever, must be favorable within 48 -72 hours. Otherwise, the patient should be re-evaluated. The criteria for hospitalization are the same as for any acute community-acquired pneumonia.
