There is no evidence that new mutant strain of SARS-CoV-2 causes a more intense illness or leads to a higher fatality rate. The main worry is that the strain is significantly more infectious than the original strain.

https://www.expresshealthcare.in/news/no-evidence-so-far-that-new-covid-19-virus-strain-more-likely-to-cause-severe-disease-or-mortality-who-dg/426508/

The new UK B1.1.7 variant. It is more efficient in transmission, but it is not necessary more virulent. From US CDC:

• Ability to spread more quickly in humans. There is already evidence that one mutation, D614G, has this property to spread more quickly. In the lab, G614 variants propagate more quickly in human respiratory epithelial cells, out-competing D614 viruses. There also is evidence that the G614 variant spreads more quickly than viruses without the mutation.
• Ability to cause either milder or more severe disease in humans. There is no evidence that VOC 202012/01 produces more severe illness than other SARS-CoV-2 variants.
• Ability to evade detection by specific diagnostic tests. Most commercial polymerase chain reaction (PCR) tests have multiple targets to detect the virus, such that even if a mutation impacts one of the targets, the other PCR targets will still work.
• Decreased susceptibility to therapeutic agents such as monoclonal antibodies.
• Ability to evade vaccine-induced immunity. FDA-authorized vaccines are “polyclonal,” producing antibodies that target several parts of the spike protein. The virus would likely need to accumulate multiple mutations in the spike protein to evade immunity induced by vaccines or by natural infection.

https://www.cdc.gov/coronavirus/2019-ncov/more/scientific-brief-emerging-variant.html

Getu Habte

From a doctor (https://twitter.com/FaheemYounus):

About New UK Strain B 117:

Bad:

-Widespread now

-50-70% more transmissible

-By increasing total cases, it causes more death

Good:

-Not inherently more lethal

-Vaccine remains effective

-We can protect ourselves by masks/avoid crowds/wash hands

There is no evidence that new mutant strain of SARS-CoV-2 causes a more intense illness or leads to a higher fatality rate. The main worry is that the strain is significantly more infectious than the original strain.

https://www.expresshealthcare.in/news/no-evidence-so-far-that-new-covid-19-virus-strain-more-likely-to-cause-severe-disease-or-mortality-who-dg/426508/

We still do not know! Studies are needed and ongoing.

Dear Getu Habte, the new mutant strain of the COVID-19 virus is 70% more transmissible but the severity and mortality are not worse than the original strain.