The UK is removing two volunteers from Africa over fears that they have come in contact with the Ebola virus in Sierra Leone.

Although neither patient has been diagnosed with Ebola, authorities are calling it a precautionary step, according to the London Evening Standard.

One of the patients, an Australian nurse, had her protective clothing punctured while working in Ebola-stricken areas. She was airlifted to Gatwick Airport south of London on Thursday.

Neither patient has shown any symptoms of the disease, which as a 21-day incubation period.

Dr. Jenny Harries, who serves as the regional director for Public Health England, said the patients present a very low risk to the public, according to the report. She said she was confident that all appropriate health actions have been taken to support them and to protect the public.

A patient was admitted to a hospital in Scotland yesterday after returning from west Africa, but tested negative for the virus. The patient, who was not identified but reported to be a woman, experienced a raised temperature but tested negative in the end.

The Australian nurse will undergo a 21-day observation period as precautionary step. She was also not identified.

A Scottish nurse who came down with Ebola is receiving treatment in London’s Royal Free Hospital. She is in stable condition after formerly being listed in critical condition. She will remain in isolation after she contracted the disease from helping patients in Sierra Leone with the organization Save the Children.

The Ebola virus is a deadly disease that has killed thousands in the West African nations of Sierra Leone, Liberia, and Guinea. There have been more than 20,000 reported cases of the virus resulting in more than 8,000 deaths as of Jan. 12.

The virus spreads through contact with bodily fluids, which can happen when an individual comes into contact with a contaminated item or surface, although spreading through the air is deemed unlikely.

The length of time between exposure to the virus and the development of the symptoms can be as little as two days but up to 21 days, which is why there is a 21-day isolation period for those who are believed to have come into contact with the virus.

Symptoms typically include fatigue, fever, weakness, reduced appetite, pain in the muscles and joints, headaches, and a sore through. Vomiting, diarrhea, and abdominal pain often accompany the fever.