A doctor from Sheba Hospital in Tel Hashomer who contracted coronavirus during the month of April has now been diagnosed once again as positive for the virus, Channel 13 News reported on Thursday. According to some studies, the antibodies may only be effective for a few weeks.

After being infected in April, the doctor suffered from fever, cough and muscle aches. In May and June, she underwent additional tests, all of which came back negative. This month she was examined again after coming into contact with a confirmed case, and was found to be positive for the virus.

This is the second case at Sheba Hospital where a person who has recovered subsequently tested positive again, after a person who recovered from the virus returned to the hospital with acute pneumonia. The tests were sent to the Weizmann Institute for further study.

According to the Ministry of Health, 1,109 new cases of the virus were diagnosed since midnight. The number of active patients is 24,956, of whom 203 are in critical condition, 58 on respirators and 110 in moderate condition.

The number of deaths from complications of the disease has risen to 383. So far, about 20,000 Israelis have recovered.