>> reporter: last year, nationwide, 62% of all officer deaths in the line of duty were from covid. >> so, let's bring in matt gutman tonight. i wanted to get to this other headline. scientists are now tracking what they call a delta sub variant, a related strain in the uk, where cases are rising. there are reports tonight it's been found in the u.s., too. what do we know so far? >> reporter: david, this is one of those so-called delta-plus variants. it hass be been detected in the. it's about 6% of all cases in the uk. you mentioned it is here in the u.s. and it's of such concern that one of the former heads of the fda, scott gottlieb, wrote today, "we need urgent research to figure out if this delta-plus is more transmissible." david? >> matt, thank you. we turn next here this evening to china. that country denying reports tonight that they have tested a nuclear-capable hypersonic missile. how would you track it if it was carrying a nuclear weapon?