Since recurrences are unusual in Kawasaki disease, it is thought that the trigger is more likely to be represented by a single pathogen, rather than a range of viral or bacterial agents. Various candidates have been implicated, including upper respiratory tract infection by some novel RNA virus. Despite intensive search, no single pathogen has been identified. There has been debate as to whether the infectious agent might be a superantigen (i.e. one commonly associated with excessive immune system activation). Current consensus favors an excessive immunologic response to a conventional antigen which usually provides future protection. Research points to an unidentified ubiquitous virus, possibly one that enters through the respiratory tract.Seasonal trends in the appearance of new cases of Kawasaki disease have been linked to tropospheric wind patterns, which suggests wind-borne transport of something capable of triggering an immunologic cascade when inhaled by genetically susceptible children. Winds blowing from central Asia correlate with numbers of new cases of Kawasaki disease in Japan, Hawaii, and San Diego. These associations are themselves modulated by seasonal and interannual events in the El Niño–Southern Oscillation in winds and sea surface temperatures over the tropical eastern Pacific Ocean. Efforts have been made to identify a possible pathogen in air-filters flown at altitude above Japan. One source has been suggested in northeastern China. Genetics
Genetic susceptibility is suggested by increased incidence among children of Japanese descent around the world, and also among close and extended family members of affected people.
It typically involves the bulbar conjunctivae, is not accompanied by suppuration, and is not painful. This usually begins shortly after the onset of fever during the acute stage of the disease. Anterior uveitis may be present under slit-lamp examination. Iritis can occur, too. Keratic precipitates are another eye manifestation (detectable by a slit lamp, but are usually too small to be seen by the unaided eye).Kawasaki disease also presents with a set of mouth symptoms, the most characteristic of which are a red tongue, swollen lips with vertical cracking, and bleeding. The mucosa of the mouth and throat may be bright red, and the tongue may have a typical "strawberry tongue" appearance (marked redness with prominent gustative papillae). These mouth symptoms are caused by necrotizing microvasculitis with fibrinoid necrosis.Cervical lymphadenopathy is seen in 50% to 75% of children, whereas the other features are estimated to occur in 90%, but sometimes it can be the dominant presenting symptom. According to the diagnostic criteria, at least one impaired lymph node ≥ 15 mm in diameter should be involved. Affected lymph nodes are painless or minimally painful, nonfluctuant, and nonsuppurative; erythema of the neighboring skin may occur. Children with fever and neck adenitis who do not respond to antibiotics should have Kawasaki disease considered as part of the differential diagnoses.