Abstract
Background:
The Influenza A Virus subtype H9 is enzootic in portions of North and Central Africa, the Middle East, and Asia, where it significantly reduces the chicken industry's profitability. The H9N2 virus was reported in Indonesia in late 2016 causing decreased egg production and increased mortality. Research on the H9N2 virus is very important as an early warning of reassortment with potentially pandemic viruses such as the HPAI virus subtype H5N1.

Aim:
This study is a tracking study aimed at isolating and identifying the H9N2 virus in laying hens from samples from 2011-2018 in Indonesia.

Methods:
Sequencing was performed on 2949 samples obtained from tracheal and cloacal swabs after they were examined for the H9N2 virus using real-time reverse transcriptase-polymerase chain reaction (RT-qPCR).

Results:
One positive sample came from West Java in 2017. The results of phylogenetic analysis revealed that this virus belongs to the China-Vietnam-Indonesia (CVI) lineage and is related to the A/chicken/West Java/VSN791/2017(H9N2) and A/chicken/Viet Nam/QN-2576/2015(H9N2) viruses.

Conclusion:
As an early warning system for AI outbreaks, active surveillance is still required to track the progress of LPAI viruses like H9N2.

Key words: Chickens, Indonesia, Influenza, H9N2, Virus