A worker disinfects public buses at the Montgomery County Division of Fleet Management Equipment Maintenance and Transit Operation Center March 20 in Rockville, Maryland. Chip Somodevilla/Getty Images

Ground zero of the novel coronavirus pandemic is in Wuhan, China but it's epicenter -- where the majority of new cases are popping up -- is a moving target, shifting globally as the virus spreads.

Europe is the current epicenter, and Italy in particular -- the country is nearing 70,000 cases and 7,000 fatalities, according to a tally by Johns Hopkins University.

But Italy's rate of new infections and fatalities could slow as the calendar ticks closer to two weeks since the country went on lockdown. Experts say that since Covid-19 is believed to have an incubation period ranging from one to 14 days, it takes those full two weeks to see the benefits of any measures advising or ordering people to stay at home.

Italy went on total lockdown on March 13 -- meaning Friday will be two weeks since the measure came into force. US states began enacting their own drastic travel restrictions in recent days, but nothing has been federally mandated.

According to CNN's tally of US cases, there were at least 52,976 cases of the novel coronavirus in the United States as of Tuesday night, and more than 700 people have died. The tally is based on numbers of confirmed cases provided by state and local health departments. CNN's tally of total confirmed cases has increased by at least 23% each day since March 4 -- in some cases, much more steeply. From March 18 to March 19, confirmed US cases rose 51% in just one day, from 8,760 to 13,229, the largest one-day increase in recent weeks.

But public health experts, including the US surgeon general, have warned the worst is yet to come.