Early research indicates the new variant is no more lethal but 10x more contagious. 

The coronavirus is mutating – The Washington Post:

Studying both versions of the gene using a proxy virus in a petri dish of human cells, Choe and her colleagues found that viruses with the G variant had more spike proteins, and the outer parts of those proteins were less likely to break off. This made the virus approximately 10 times more infectious in the lab experiment.

The mutation does not seem to lead to worse outcomes in patients. Nor did it alter the virus’s response to antibodies from patients who had the D variant, Choe said, suggesting that vaccines being developed based on the original version of the virus will be effective against the new strain.

(Note that all of this is based on early, preprint research. Nothing here has been peer reviewed as yet.)