A 34-year-old accountant returns home after a trip to Calcutta, complaining of malaise, fatigue, and loss of appetite. Three months after initial diagnosis, the results of serological tests reveal: HBcAb, positive; HBeAb, positive; HBeAg, negative; HBsAg, negative; HBsAb, negative. The absence of HBsAg and HBsAb from the serum of this patient is reflective of which of the following?