Four people have died on Holland America's Zaandam ship, at least two of them from the coronavirus. Nine others have tested positive and 179 more have flu-like symptoms.
Some of the first warning signs can include extreme fatigue, weakness and chills. But other symptoms often follow.
"In the next few days we will reach 1 million confirmed cases, and 50 thousand deaths,” the World Health Organization's Director-General warned.
Martha's Vineyard asked seasonal residents not to come to the island to escape the coronavirus. Many did anyway, and now the small island has eight cases.
"It's difficult to help them understand what's going on," a foster father said. "Sometimes even we don't understand."