COVID Risk Increases in Boston, Most of Eastern Mass.

Five new Massachusetts counties jumped from low to medium risk for COVID-19, according to the latest data from the Centers for Disease Control and Prevention.

A week ago, only Dukes County -- which includes Nantucket and Martha's Vineyard -- were in the medium risk category. But this week, Dukes County jumped into the high risk category and Barnstable, Middlesex, Suffolk, Norfolk and Plymouth counties all went from low to medium risk. The rest of the state remains in the low risk category.

Over the past month, risk levels had been steadily declining across Massachusetts, but the latest round of data shows the risk starting to tick up again.

The news remains mostly positive across the rest of New England, however, with two states entirely in the low risk category.

New omicron subvariant rising in Massachusetts

The rising risk level in Massachusetts comes as the highly-contagious BA.5 subvariant is becoming more prevalent in the state and cases have begin to climb once again.

Massachusetts health officials reported 1,699 new COVID-19 cases and 18 new deaths on Thursday. The state's seven-day average positivity was at 7.29%, which is up from 5.85% a week ago but still far lower than it was a month ago.

What are symptoms for COVID-19 subvariant BA.5?

The CDC has listed omicron subvariant BA.5 as a variant of concern as it continues to become more prevalent across the U.S, including in parts of Massachusetts and New England.

The most common symptoms of subvariant BA.5 include a runny nose, sore throat, headache, persistent cough and fatigue.

Francois Balloux, the director of the University College London Genetics Institute, told NBC News that no difference has been observed so far between BA.4 or BA.5 symptoms and those of previous subvariants.

COVID risk levels across New England

Connecticut and Maine saw slight increases in COVID risk over the past week, but across the rest of the region the risk levels remain quite low.

Maine, which was entirely low risk a week ago, saw Aroostook County in the far northern part of the state return to the medium risk category.

All of New Hampshire remains in the low risk category for the second straight week.

Vermont's Bennington and Rutland counties are still medium risk, but the rest of the state is in the low risk category.

All of Rhode Island is now at low risk.

In Connecticut, Fairfield, Litchfield, Middlesex and New Haven counties are in the medium risk category, but the rest of the state is low risk.

Residents in counties with high risk are urged to wear masks indoors in public and on public transportation, to stay up to date with vaccines and to get tested if they have symptoms, according to the CDC.

Residents in areas with medium risk are encouraged to wear a mask if they have symptoms, a positive test or exposure to someone with COVID-19. Anyone at high risk for severe illness should also consider wearing a mask indoors in public and taking additional precautions, the CDC says.