FILE PHOTO: Amit Shah, President of India's ruling Bharatiya Janata Party (BJP), addresses supporters during a public rally at Bhaat village on the outskirts of Ahmedabad, India October 16, 2017. REUTERS/Amit Dave

NEW DELHI (Reuters) - The chief of India’s ruling party, Amit Shah, will be discharged from hospital in a day or two after a bout of swine flu, a party spokesman said on Thursday.

It is not clear how Shah, a key lieutenant of Prime Minister Narendra Modi, contracted the H1N1 influenza.

“AmitShah is doing well. He will be discharged in a day or two. Thanks everyone for your good wishes!”, Anil Baluni, spokesman of the ruling Bharatiya Janata Party said in a tweet.

Health officials said lower than normal temperatures this winter have led to a spike in cases of swine flu in northern India.

“Cases of seasonal swine flu in India go up during winters and this January the winter is proving particularly harsh,” said R. S. Taneja, the head of the medicine department at Delhi’s Ram Manohar Lohia hospital.

Overall, though, the National Centre for Disease Control said 13,447 cases of H1N1 virus were reported by Dec. 9 of last year compared to 38,811 in 2017.

Shah is the second top member of Modi’s inner circle to fall ill. Finance Minister Arun Jaitley left for the United States earlier this week for a medical check-up, officials said. They did not provide details of his condition.