According to Official Guinness Records,
The longest handshake relay consists of 1,730 participants, achieved at an event organised by Dr Shahul Hameed KP, AIROCIS College of Aviation and Noble group of schools (all India) in Kerala, India, on 12 January 2018. This record has remained unbroken since 2013.
For a complete list of 2018 records, please visit 2018 Guinness Records in India.