Researchers at Chung-Ang University Hospitals (CAUH) have found that mutated version of the rotavirus has increased after the vaccination became available in Korea in 2007, the hospital said Friday.

Rotavirus is a virus that can cause acute gastroenteritis in infants under the age of five. Its symptoms include vomiting, fever, and dehydration. The World Health Organization (WHO) has designated the virus as one of the top-priority contagion diseases that needs eradication.

Korea had introduced RotaTeq, developed by MSD, in 2007, and Rotarix, developed by GSK, in 2008 to combat virus infections. Since the introduction of the two vaccines incidence of rotavirus has been decreasing.

However, the research team, led by Professor Lim Im-seok of the department of pediatrics at the hospital, revealed there were more cases of a different mutated genotype of the rotavirus, after analyzing rotavirus infections cases at the hospital from 2013 to 2015,

In the past, there was a lot of 'G1P [8] genotype' rotavirus. During the period the team analyzed, however, there were far more cases with patients infected with the 'G2P [4] genotype' rotavirus.

The team discovered that the G2P [4] genotype rotavirus increased as most primary gene type and some of the 11 viral RNA genomes recombined with animal virus genomes, such as cattle or goats. They also found virus mutations in 17 to 24 amino acid sites in vaccine and antigenic determinants currently used.

“The mutations observed in this study were due to either natural mutations or recombination between human and animal varieties,” the team said in a statement. “We hope that the findings will reveal the mechanism of the causative agent of rotavirus infections, the causes of new and mutated rotavirus infections, and provide important information on the development of efficient rotavirus vaccines in the future.”