A Japanese survey has found that 97 percent of people who developed a fever while living with COVID-19 patients tested positive for the coronavirus.

A public health office in Ibaraki Prefecture, near Tokyo, conducted the survey in January and reported the results to the health ministry's panel of experts.

The heath office surveyed 107 people living with someone confirmed to be infected with the coronavirus between January 4 and 22 and who developed some sort of symptom.

Of them, 75 developed a fever, and 97.3 percent of them tested positive for the virus.

The remaining 32 developed other symptoms, such as coughing, and 68.8 percent of them tested positive.

Japanese doctors are currently allowed to diagnose people classified as close contacts of COVID-19 patients as being infected without testing when they have a fever or other symptoms.

The public health office notes that when such people have a fever, they are likely to test positive and a doctor's diagnosis will probably be accurate in most cases.

However, it advises people with no fever to have a coronavirus test to confirm if they are actually infected, before starting medication or refraining from going out.

As the hay fever season in Japan approaches, the head of the health office says some people may develop similar symptoms due to pollen allergy rather than coronavirus.