Groton — Noting that trends in coronavirus infection rates and hospitalizations "have indicated the virus has been adapting and its reach growing," the Naval Submarine Base in Groton announced Wednesday afternoon it is increasing its Force Health Protection Condition, or HPCON, from Alpha to Bravo, effective immediately.

HPCON Alpha is for limited community transmission, whereas Bravo is moderate, Charlie is substantial and Delta is severe.

Sub base spokesperson Chris Zendan said the direction to increase HPCON comes from the commander of Navy Region Mid-Atlantic and the commanding officer of the sub base, and is mandated by the Office of the Secretary of Defense guidance.

"All of us — immunized or not — must remember that the pandemic continues, and our Navy and SUBASE bottom line must always be: ensuring we do not raise any undue risk to our Sailors, our families, and our critical mission," Commanding Officer Capt. Todd Moore said in an email statement.

Zendan said the sub base had been in HPCON Alpha since June 10. The transition to HPCON Bravo means gathering size may be limited in events and large activities, such as at the gymnasium, the sub base said in a Facebook post. The racquetball courts are closed until further notice, and use of the pool will require appointments.

Mask requirements remain in effect at the clinic, Child Development Center and Youth Center, and for people on base who aren't fully vaccinated.

The sub base said event organizers will post any new capacity restrictions and work with the emergency management team concerning any requests for exceptions. Additionally, commanding officers may require some military personnel to follow more restricted guidance.

"The shift results from review of local COVID-19 virus conditions as tracked and reported by state and community health departments," the Facebook post said.

The sub base noted that Connecticut reported its highest COVID-19 positivity rate since late May on July 14, and the local infection rate per 100,000 people has begun to grow. The sub base said these trends are attributed to virus variants, especially the delta variant, and the "overwhelmingly majority of those individuals impacted are those who are NOT vaccinated."

"The base increase to HPCON Bravo should serve as reminder to all that the pandemic remains significant, and even deadly, for those who are not vaccinated," the sub base said.

According to Gov. Ned Lamont's office, the COVID-19 test positivity rate Wednesday was 1.95%, and 58 people statewide were hospitalized with COVID-19.

By comparison, hospitalizations peaked at 1,972 in April 2020, hit a pandemic low of 25 on July 9, and have been trending upward since. Connecticut had reported a test positivity rate of 0.35% on June 14.

e.moser@theday.com