Cholera bacteria becoming more deadly

The cholera bacterium is more deadly today than previous types have been, scientists recently reported, and they have urged that vaccinations be given immediately in the case of an outbreak.

In a series of studies in the journal Public Library of Science, a team of researchers discovered that a hybrid cholera strain has gone through two major changes in the last 20 years, making it increasingly fatal and causing longer outbreaks, according to Xinhua.

The first major mutation allowed the bacterium to infect people who were thought to be immune because they had been exposed to a previous strain. According to Edward Ryan of Massachusetts General Hospital and Harvard University, the second change caused the bacterium to be more dangerous.

"Cholera caused by the hybrid strain may be more clinically severe and...may explain why we are seeing case fatality rates of one to five percent in recent outbreaks as opposed to under one percent historically accepted as the goal for response teams," Ryan wrote, according to Xinhua.

Mass vaccination programs are now recommended even after an outbreak has begun, according to some studies.

Experts have disagreed in the past about the effectiveness of vaccinating once an outbreak has started. Many have cautioned it is best to focus on rehydrating the sick and providing safe water and good sanitation.

The recent outbreak in Haiti has refocused the debate. More than 2,000 people have died of cholera and at least 105,000 have fallen ill, Xinhua reports.