At least six US states have ordered schools to close in an attempt to curb the spread of the new coronavirus which has infected more than 1,660 people across the country.

Schools in Ohio, Michigan, Oregon, Maryland, Kentucky and New Mexico were told to shut from Monday for at least two weeks, affecting millions of students and likely to cause problems for many low income families who rely on free or subsidized school meals.

"This is a necessary step to protect our kids, our families, and our overall public health," Michigan governor Gretchen Whitmer said in a statement Thursday night announcing the closure of the state's schools until April 6.

Kentucky governor Andy Beshear recommended schools close for at least two weeks and the state was making arrangements to continue feeding children from low income families.

Nearly 75 percent of the 650,000 children attending public schools in Kentucky are eligible for free or reduced-price meals, according to the state education department.

Maryland governor Mike Hogan closed schools for two weeks and banned all gatherings of more than 250 people among a series of measures to tackle the coronavirus.

"This problem continues to evolve and will escalate rapidly and dramatically," Hogan said.

"For Marylanders, the actions I have announced here today will be disruptive to your everyday lives. They may seem extreme, and they may sound frightening. But they could be the difference in saving lives and keeping people safe."

In Oregon, governor Kate Brown said they had tried to keep schools open but "it has now become impossible to functionally operate schools due to workforce issues and student absences." Schools there will close until the end of March.

New Mexico governor Michelle Lujan Grisham said schools in her state would also shut for three weeks.

"This is a proactive measure to limit the potential community spread of COVID-19," said New Mexico education secretary Ryan Stewart.

"We have seen other states take this measure after they have experienced community spread of this virus. New Mexico is going to be proactive and do everything we can to prevent the potential spread of the virus."

Ohio Governor Mike DeWine ordered schools to close for three weeks but said they should find alternative ways to provide classes. Ohio has also banned gatherings of more than 100 people.

"We want to thank educators and administrators for the extraordinary efforts they will take to continue offering services during this time of national crisis," DeWine said.

Washington state, which has recorded 31 of the 40 coronavirus deaths in the US, according to Johns Hopkins University, has also closed all schools in three counties in the Seattle area through April 24.AFP