New York City, with more cases and deaths than anywhere, follows a similar curve.
From NYC Health: Daily deaths from 3/15 to 5/17 (dark blue is confirmed, light blue projected)
COVID-19: Data Summary - NYC Health
So some say these curves are caused by lockdowns, but some countries like Sweden never really locked down, and others that started opening up a month ago are not showing huge spikes in new cases and deaths.
We know that covid 19 is more infectious than common flu, about twice as much, even the H1N1 flu. But yearly influenza infections dwarf what covid 19 has done in terms of infections. On average, 30 million Americans get the flu each year, and we have partially effective vaccines for the flu. It's possible that there will be a second wave and covid 19 will rack up higher numbers, but nobody knows for sure. SARS, a similar coronavirus, was global and then just faded away, has not returned. They don't know exactly why.
• Number of flu cases U.S. 2010-2017 | Statista
So why is this virus, more infectious than even the most virulent strains of the flu, not infecting and making more people sick? A recent antibody test was done in New York which estimated 21% of New Yorkers had been infected, but never got sick, called their Doctor, and got a test confirming the disease. They were immune in some way.
So what does all this mean? Perhaps a large portion of the population does indeed have some kind of immunity, possibly from previous exposure to other coronaviruses like the common cold, and this immunity is stronger in younger, healthier individuals who rarely die if infected.