The hospital said it is too early to say that the patient is out of danger.
The police officer leading the investigation into the latest Novichok poisoning in the United Kingdom has said he does not know if it will ever be possible to establish a definitive link between the most recent poisoning and that of Sergei and Yulia Skripal last March.
'We sincerely apologise if any offence was caused, especially to the families of Dawn Sturgess and Charlie Rowley, and understand the timing of the release of this product may have lacked sensitivity.
They both then fell ill on Saturday 30 June, and Ms Sturgess died eight days later.
Britain blamed the Russian state for the attack on Sergei Skripal and his 33-year-old daughter - an allegation Moscow has repeatedly denied.
Police searching for the source of a Russian nerve agent that killed a woman and sickened three others have seized a vehicle about 40 miles away from the original investigation site.
Dawn Sturgess died after being exposed to the nerve agent Novichok.
The backdrop to this meeting was British but the issue was global as police issued a Novichok warning to the residents of Salisbury.
Basu said Tuesday police have found no forensic link between the two cases, and it was possible that a link would never be established, the Guardian reports.
Russian Federation was accused of targeting the Skripals in March but has denied involvement.
"The brutal reality, however, is that I can not offer you any such assurances or guarantees at this time".
He said no one else in the Amesbury and Salisbury region, where the couple lived in southwestern England, has shown any sign of Novichok poisoning.
Police now believe the two handled a contaminated item with a high dose of Novichok, although they have not been able to confirm if it was from the same batch as the one used in the attempted murder of the Skripals.
Ms Sturgess collapsed at about 10:15am and was taken to hospital in an ambulance and Mr Rowley was taken to hospital later that day.
A tweet by police said, "the public should not be alarmed by this".