Dr Michael Jacobs, the Infectious Diseases Consultant treating the nurse, earlier warned signs of improvement in Ms Cafferkey's health did not indicate that she would make a full recovery.
'The next few days are critical, things could get worse, but in a week's time we will know a lot more about where we stand,' said Dr Jacobs on Tuesday.
Earlier this year nurse Will Pooley recovered from the illness at the same isolation unit where Ms Cafferkey is being treated, after being given the drug ZMapp.
William Pooley, the first Brit to be diagnosed with Ebola, made an impassioned Christmas Day plea to the nation to help in the fight against the deadly virus.
Speaking in Channel 4's Alternative Christmas Speech, the 29-year-old nurse pleaded with viewers to consider how they could help battle the illness which has claimed more than 7,000 lives.
Protocol in place at Heathrow Airport was slammed as 'shambolic' after it was revealed the nurse complained of a fever, but was allowed to board a flight to Glasgow despite having her temperature taken six times in one hour.