It said: “We are operating a reduced timetable until further notice to ensure we can run as reliable a service as possible with the ongoing impact of coronavirus isolation and sickness.”
Commuters are advised to ‘plan and re-check’ their journeys before travelling.
Southern said that from Monday (January 17) the following will operate:
A service will operate at peak times, calling at all stations between London Victoria and Crystal Palace/Birkbeck via Balham.
Between about 7am and 8pm, one train per hour between London Victoria and Bognor Regis/Southampton Central via Horsham.
All other services will continue to operate to and from London Bridge or will only operate south of Balham.
For those travelling between London Victoria and stations towards East Grinstead, Gatwick Airport and the Sussex Coast, please change at East Croydon.
Visit southernrailway.com to find out more.