The United States has now lost over 600,000 mothers, fathers, children, siblings and friends to Covid-19, a painful reminder that death, sickness and grief continue even as the country begins to return to something resembling pre-pandemic normal.

The United States passed 600,000 COVID-19 deaths on Monday, about 15 per cent of the world's total coronavirus fatalities of around 4 million, a Reuters tally shows.

The rate of severe illness and death has dropped dramatically as more Americans have become vaccinated, creating something of a psychological whiplash that plagues the millions whose lives have been touched by the disease.

Many are eager to emerge from more than a year of sickness and lockdown, yet they still suffer — from grief, lingering symptoms, economic trauma or the isolation of lockdown.