The highest flu levels were recorded in the centre of Switzerland, Ticino and Graubünden, the federal office of public health (FOPH) said this week.
In these cantons 154 consultations for flu per 100,000 residents were recorded by doctors in the first week of the year, the FOPH said.
The average for the country was 53 consultations.
The flu season typically continues for about 14 weeks, peaking in mid-February, according to government charts.
The only area of the country with negligible flu activity was in the cantons of Basel-City, Basel-Country, Aargau and Solothurn.
The health office has set a threshold for an epidemic of influenza-like illness at 68 consultations per 100,000 people.
Last winter, Graubünden and Ticino experienced an epidemic that saw flu consultations rise to more than 800 per 100,000 residents, the highest in the country.
It's too early to say whether this year will see a repeat of that level of outbreak.
Since 1986, the FOPH has established the “Swiss Sentinel Surveillance Network” that gauges levels of flu, the mumps, rubella, pertussis, otitis and pneumonia.
This is based on data submitted weekly by 150 to 250 general practitioners, internists and paediatricians.