Explainer: What is a second wave of a pandemic, and has it arrived in the U.S.?

Counselors sanitize as children receive temperature checks to prevent the spread of coronavirus disease (COVID-19) at Carls Family YMCA summer camp in Milford, Michigan, U.S., June 23, 2020. REUTERS/Emily Elconin

CHICAGO (Reuters) - Infectious disease experts, economists and politicians have raised concerns about a second wave of coronavirus infections in the United States that could worsen in the coming months.

But some, including Dr. Anthony Fauci, the U.S. government's top infectious disease expert, said it is too soon to discuss a second wave when the United States has never emerged from a first wave in which more than 120,000 people have died and more than 2.3 million Americans have had confirmed infections with the novel coronavirus.