What is primary complex? Primary complex is an infection due to the mycobacterium Tuberculosis bacteria. This is mainly characterized by weight loss or very slow in gaining weight, presence of nodes especially in the neck area. Most children are asymptomatic but it is confirmed through ppd or mantoux test. By taking the anti-tb meds religiously children will be completely cured after 6 months of treatment course. Be sure not to escape taking it for better compliance of the medication.