It is known that many infectious diseases have seasonal distributions, and high incidences of infectious diseases mostly occur in winter. 16 Some virus infections are positively correlated with serum anti-ds-DNA antibody titers of patients with SLE. 17 A high incidence of virus infection of the respiratory tract occurs in winter and spring. In order to eliminate the influence of infection factors on seasonal distribution of active SLE, patients who had active SLE combined with an infection were excluded from the study. Therefore, it can be discounted that infection causes a high incidence of active SLE in the winter and a low incidence in the summer.