The county has averaged about 17 new cases per day over the last 14 days, according to a 14-day moving average graph updated weekdays by the health department.
And, according to the state Department of Health's risk assessment data, the county has had 75.9 cases per 100,000 population during the past two weeks - September 28 to October 11 - which puts the county in the "high transmission" range.
She said the latest figures also showed the number of deaths had continued to increase.
Chief Medical Officer Dr Tony Holohan said that Level Five restrictions were necessary because the disease is at "very serious levels in our country and posing significant risk to public health".
There are 2,273 individuals who have a positive viral antigen test and are considered probable cases and 648 individuals who have a positive serology test and either COVID-19 symptoms or a high-risk exposure. Stay at home - don't go to work, don't go to school.
Dr Holohan added: "If you live with someone who has Covid-19 or you have been told that you are a close contact, you must restrict your movements for a full 14 days".
It also emerged this week that 2,500 people positive for Covid-19 were asked to carry out their own contact tracing as the tracing system was overwhelmed.
Approximately 11,906 of our total cases are among health care workers.
Professor Philip Nolan said the reproduction number was between 1.3 and 1.4 nationally.
Twenty-three people are hospitalized in Missoula County including 12 county residents.
It's now more than 100 times higher than it was during the summer.
Tom Wolf said earlier this week that the state is experiencing a "fall resurgence" of coronavirus.
Less than five cases are being reported in Carlow with the 14-day rate staying at 242 per 100,000 population.
Prof Nolan said they were catching milder and asymptomatic cases now and in a younger cohort who were less likely to be admitted to hospital and less likely to die, but he said they did not know the long-term effects they would suffer.