Newborn screening (NBS) of cystic fibrosis (CF) is not available currently in Hungary. Pediatricians should be able to recognize the illness based on the symptoms alone. Lack of NBS causes differential diagnostic challenges for physicians and delayed diagnosis of CF. We present a case of a two-year-old girl who was transferred to our hospital as a suspected Covid-19 patient with one week history of fever and coughing in March 2020. As Covid-19 was excluded, the severity of the clinical picture pointed towards an acute exacerbation of an underlying chronic condition. Her symptoms such as tachypnea, wheezing, lung crackles, hepatomegaly and clubbing of the fingers were all consistent with undiagnosed CF. In the end, sweat chloride level and genetic test verified the diagnosis. This case emphasizes the need of NBS in Hungary.