The Good Morning Britain star's husband, 53, has spent the last 214 days confined to a hospital bed and despite no longer testing positive for the deadly disease, he remains seriously ill.
Kate has now revealed that Derek has been able to speak for the first time, whispering the word "pain" to his wife, who watched on "in tears" over FaceTime.
WATCH: Kate Garraway fears she is boring viewers with updates on husband Derek
"We have had a breakthrough which was both amazing yet heartbreaking," Kate, 53, told The Sun. "It happened when the nurses were moving Derek, as part of his treatment, to trigger the sensation of gravity because he's been horizontal for so long.
"As they were shifting him, they asked if he could feel anything — not expecting a response as he hadn’t previously. But suddenly he mouthed in a whisper, 'Pain'.
Derek was admitted to hospital on 30 March
"Obviously it’s so heart-wrenching that his first word was 'pain', but it is a huge breakthrough because it means he has been able to connect the feeling in his body to his brain and mouth."
Kate added: "They called me straight after and I burst into tears. The staff told me later that they were so emotional as well.
"It breaks my heart that there may have been times that he’s been in terrible pain and wasn’t able to communicate it. He’s said it twice now and I was there for the second one, watching him over FaceTime.
The couple are proud parents to children Darcey and Billy
"Of course there’s a big difference between being able to say the word ‘pain’, and Derek being the Derek I know and love. But I feel in his eyes that he’s there, and that we just have to hold on in this grim battle."
Kate's update on Derek's health comes after it was reported that she is set to appear in a poignant ITV documentary about the coronavirus pandemic and the effect it has had on her and her family.
The news of the one-off special was confirmed on Thursday's Lorraine. It is expected that Kate will speak to survivors of the disease, as well as NHS workers on the frontline.
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