Immunodeficiency should be suspected when recurrent infections are the following: Severe Complicated In multiple locations Refractory to standard treatment, ie, require multiple courses of oral antibiotics or any need for IV antibiotics to resolve Caused by unusual organisms Present in family members Initially, infections due to immunodeficiency are typically upper and lower respiratory tract infections (eg, sinusitis, bronchitis, pneumonia) and gastroenteritis, but they may be serious bacterial infections (eg, meningitis, sepsis).