The state also reported two more COVID-19 fatalities between Sunday and Monday, which took the death toll to 39, he said.
A 57-year-old policeman, who returned from West Bengal after poll duty in April, has succumbed to the infection at Zoram Medical College (ZMC) at around 8:30 am on Monday, he said.
The patient was diagnosed with COVID-19 on May 4 and had comorbidities.
Besides, an 87-year-old man with comorbid status also died of Covid-19 soon after he was diagnosed with Covid-19 on Sunday, he said.
At least 744 samples were tested for Covid-19 in the last 24 hours and 13.30 per cent of them came out positive for COVID-19.
Of the 99 fresh cases, 83 cases were reported from Aizawl district, 3 from Siaha district, 4 from Kolasib district, 8 from Lawngtlai district and 1 case was reported from Lunglei district, the official said.
More than 25 children and two frontline workers were among the newly-infected people, he said.
All the 99 patients were found to have locally contracted the virus and among them, the contact history of 23 patients are yet to be ascertained, he said.
Seventy-four patients have developed symptoms of COVID-19, while 25 are asymptomatic.
The number of active cases now stands at 3,033, while 9,015 people have recovered from the infection.
As many as 152 people have recovered on Sunday. The recovery rate is 74.59 per cent.
Mizoram has tested 3,89,751 samples for COVID-19 till date.