Symptoms vary rapidly, perhaps even by the hour, and there is a rapid return to the premorbid state of health." A frequently quoted authority on BD, P. Pichot (Hôpital Sainte Anne, Paris) provides this description of BD: 

sudden onset: a bolt from the blue. manifold delusions without recognizable structure and cohesiveness with/without hallucinations. clouding of consciousness associated with emotional instability. absence of physical signs. rapid return to pre-morbid level of functioning.Pichots criteria can be refined further with these typical clinical characteristics: 

age: usually between 20 and 40 years of age. onset: acute without prior mental illness (with the exception of previous episodes of bouffée délirante). past history: no chronic mental disturbance after resolution of the BD episode. typical symptoms: delusions and/or hallucinations of any type. Depersonalization/derealization and/or confusion
depression and/or elation. symptoms quite variable from day to day and even hour to hour. not due to alcohol, drug use, or organic mental disorder. Formal classification
In 1968 the French national organization INSERM (Institut National de la Santé et de la Recherche Médicale) classification of mental illness referenced two types of BD in their category acute delusional psychoses and confusional states viz. reactive bouffée délirante and bouffée délirante (Magnans type). This classification scheme has been largely replaced by the two nosological systems discussed below.
The World Health Organization edition of the International Classification of Diseases 10th edition:version 2019 (ICD-10,  CIM-10 en français), lists BD as the subentry "Bouffée délirante without symptoms of schizophrenia or unspecified" under diagnosis code F23: Acute and Transient Psychotic Disorders subsection, F23.0: Acute polymorphic psychotic disorder without symptoms of schizophrenia. It is likely that the use of the term BD in French clinical psychiatry will decline further with the proposed 2022 implementation of ICD-11 (which was released in May 2019.) In contrast to the ICD-10, the term BD does not appear anywhere in ICD-11. The closest clinical match for BD in the ICD-11 is code 6A23, Acute and transient psychotic disorder which is defined as

acute onset of psychotic symptoms that emerge without a prodrome and reach their maximal severity within two weeks. Symptoms may include delusions, hallucinations, disorganization of thought processes, perplexity or confusion, and disturbances of affect and mood. Catatonia-like psychomotor disturbances may be present. Symptoms typically change rapidly, both in nature and intensity, from day to day, or even within a single day. The duration of the episode does not exceed 3 months, and most commonly lasts from a few days to 1 month. The symptoms are not a manifestation of another health condition (e.g., a brain tumor) and are not due to the effect of a substance or medication on the central nervous system (e.g., corticosteroids), including withdrawal (e.g., alcohol withdrawal).