A Northern Virginia middle school canceled a seven-day visit by 21 Chinese students and their chaperones on the day they arrived in the United States because of fears over a new coronavirus circulating in China, according to a school letter emailed to parents Wednesday afternoon.

The students, who landed Wednesday in New York, had planned to take a bus to Longfellow Middle School in Fairfax County for the exchange program and meet with their host families Wednesday evening. But in the letter sent to families at the school, Longfellow Principal Carole Kihm said that the exchange trip was being altered “out of an abundance of caution” and that the students would no longer visit the school.

“Student and staff health and safety remain our first priority,” Kihm wrote. “While health officials believe the risk of illness transmission of the novel Coronavirus from these students is extremely low, we felt it necessary to make this adjustment.”

The visiting students are from Yichang, about 175 miles west of Wuhan, where the outbreak was first detected. Authorities in China reported Wednesday that 17 people have died from the infection, and more than 470 people are confirmed as having the pneumonialike illness. Yichang and Wuhan are in Hubei province, where almost all of the infections with the new coronavirus have been reported.

Fairfax County Public Schools and the Fairfax County Health Department initially sought to reassure parents that the students from China were extremely unlikely to have been affected by the virus.

In an email sent to Longfellow families Tuesday evening, the school district and health department said that no cases of the coronavirus had been reported in Yichang and that Longfellow students would not be in jeopardy.

“Based on guidance from the Fairfax County Health Department, in conjunction with the Centers for Disease Control and Prevention and the Virginia Department of Health, there is no increased risk in our school at this time,” the email stated.

But several parents at the school contacted Fairfax County Public Schools officials to express concern about the virus and about having the students visit.

During an emotional meeting at the school Wednesday morning, parents expressed doubts about how well officials were able to assess the risk, according to a parent who spoke on the condition of anonymity because of the sensitivity of the matter. They asked for the trip by the visiting students to be canceled.

School officials moved Wednesday afternoon to cancel the trip and said they would try to arrange a program for the visiting students with the travel company to “facilitate cultural and educational activities in the DC area so that the students enjoy a positive experience.”

Fairfax County Public Schools spokeswoman Lucy H. Caldwell said that the Chinese students will stay at an area hotel and that the school system “is looking at ways to facilitate virtual instruction or interaction between the visiting students and Longfellow students.” The district did not provide any statement from the chaperones of the Chinese students about their reaction to the trip’s cancellation.

Before the trip, the Chinese and American students had exchanged emails and photographs to get to know each other. One of the host family members, who also spoke on the condition of anonymity, expressed “great disappointment” that the trip had been canceled.