Mers Virus news, update: A virulent and highly fatal pathogen that’s on the rise, the MERS virus derived from its name Middle East Respiratory Syndrome, has risks and concerns that is still unknown.

According to the Huffington Post, the biggest concern about the disease lies in the basic information that they still don’t have about it. A recent report by the World Health Organization (WHO) said that 75% of the new infections were transmitted between humans alone.

The virus is closely related to SARS, which spread rapidly across Asia a decade ago and left an estimated 800 people dead. Based on current stats, MERS has a higher fatality rate than SARS and no known vaccine or cure. It has also proven so much less as a public health risk because its transmission rate has remained low.

The Huffington Post reports, however, that there are anecdotal hints that the disease could be bucking that trend including a dramatic uptick in the number of sick patients in Saudi Arabia where the outbreak is centered. More than 400 people have been infected with the disease so far, almost all of them in the Middle East. The virus, which has cause “severe cute respiratory illness,” according to the U.S. Center for Disease Control and Prevention, has killed one-third of those who have contracted it, notes the Huffington Post.

The European Center for Disease Prevention and Control, as well as other official health groups, said that the risk of worldwide pandemic is low. Epidemiologists and public heath experts warn say, however, that critical blank spots in the scientific understanding of the virus need to be filled in order to be certain.