[A 64-year-old male with recurrence of herpes simplex encephalitis after suffering from severe pneumonia and sepsis].

The case is a 64-year-old male who had a past history of herpes simplex virus encephalitis (HSE) two years prior to his admission. He was admitted to our hospital due to severe pneumonia and sepsis. Several days later, he developed HSE again. It has been known that immunosuppressive state called immune paralysis occurs in the patient with sepsis due to the amplification of anti-inflammatory responses after the initial hyper-inflammatory phase, which increases the susceptibility to various latent viruses including herpes simplex virus. In the present case, we consider that the severe infection may trigger the recurrence of HSE through the viral reactivation due to immune paralysis. When we see a patient suffering from severe infection who had a past history of HSE, we should keep in mind that such a patient may have a risk of the recurrence of HSE.