A deadly bacterium is sweeping through hospitals in Israel and has already caused the deaths of up to 200 people, health officials acknowledged Wednesday.

"Between 400 to 500 people have been infected by the bug, and 30 to 40 percent of them have already died," said Yehuda Carmeli, the head of the epidemiology unit at the Sourasky Medical Center in Tel Aviv. "However, it is important to note that most of them were in a serious condition, and some were suffering from prior medical conditions."

Health Minister Ya'acov Ben-Yizri confirmed that Klebsiella pneumoniae was responsible for the deaths, but insisted that the victims were already seriously ill when they contracted the deadly bug.

Ben-Yizri said his office was investigating, and that there was no reason to panic. He added that the Health Ministry was investigating to see if other countries were encountering similar problems with the bacteria and if there were antibiotics available.

Most of those infected have been hospitalized for over 25 days, and their average age was about 75.

The bacteria is resistant to all kinds of antibiotics.

Avi Yisraeli, the ministry director-general, confirmed that nobody outside of the hospitals was in any immediate danger, but only those who are very ill are at risk.

"This is not the first time that there is a virulent strain of bacteria undefeated by antibiotics, and it is happening abroad as well," Yisraeli claimed.

Klebsiella pneumoniae is normally found in the mouth, skin and intestines and can cause pneumonia. It is generally found in patients with weak immune systems and or in the elderly.