So far, six people have died of the infection in the state.
Special Secretary (Health) Nipun Jindal said eight of the 18 fresh cases were reported from Kangra; four each from Hamirpur and Solan; and one each from Una and Kullu.
Meanwhile, nine patients--four from Kangra, two each from Hamirpur, Solan; and one from Una-- recovered from the virus, he added.
A majority of the new patients had recently returned from Maharashtra' Mumbai, Delhi and Uttar Pradesh's Noida.
In Kangra, seven of the eight new patients had returned from Delhi on May 27 whereas one returned from Mumbai, Jindal said.
Those who came from Delhi were a two-year-old boy from Mijhgran in Nurpur; a 30-year-man from Dari; a 51-year-old man from VPO Sandu in Shahpur tehsil, his 17-year-old son; a 47-year-old man from Kulhan village in Nurpur tehsil, his nine-year-old-son; and a 27-year-old man from Bari village in Khundian.
The official said they had been institutionally quarantined in Jawalamukhi and were shifted to a COVID care centre at Baijnath.
Besides, a six-year-old girl who was quarantined at Parour, tested positive for the virus on Sunday.
She had returned from Mumbai with her mother on May 24. Her mother has too tested positive for the virus.
In Hamirpur, the four fresh cases were institutionally quarantined at different places after their recent return from Delhi and Noida, Deputy Commissioner Harikesh Meena said.
They are two men, aged 23 and 40, from Jangal village; a 52-year-old man from Shashan village of Bhareri; and a 32-year-old woman from Dhamrol village.
In Kullu, a 65-year-old man from Jaon in Nirmand tested positive for the infection on Sunday, Kullu SP Gaurav Singh said.
He, along with five members of his family, had returned from Delhi on May 19.
His wife, son and daughter-in-law tested negative, the SP added.
With this, the number of active cases in the state now stands at 206 as 120 COVID-19 patients have recovered.
Hamirpur has the highest number of active cases at 80, followed by 54 in Kangra, 18 each in Solan and Una, 11 in Bilaspur, nine in Chamba, seven in Shimla, six in Mandi, two in Sirmaur and one in Kullu. DJI RDK RDK