The Health ministry announced on Feb. 15, 2018, that a high school student in Tokyo’s Suginami ward has tested positive for COVID-19. COVID-19 is found in cytomegalovirus, one of the common viruses that causes stomach illness, including haemolytic-uremic syndrome.

Samples from her gastroenterologist matched samples of other patients testing positive for the cytomegalovirus, according to Kyodo News. A high school classmate also tested positive for the virus and has been taking the same immune-suppressing treatment she is being given.

The school’s nurse said she expected over 600 students to show up on Thursday, the day after the infection was confirmed.

Kyodo News reported that 174 students have been ordered to stay home with flu-like symptoms while school authorities investigate the cause. As with the highly infectious flu, symptoms, including fever, chills, nausea, vomiting, diarrhea, muscle aches and fatigue can go without treatment, or be treated with antibiotics, but it is more dangerous to others to not be treated.

Some students have been sent to the hospital with intestinal and lung infections.

“I went home about a week ago, but I kept moving when I could,” Ms. Takaya said. “I ended up feeling sicker and sicker over the time.”

Ms. Takaya went to the hospital on Wednesday, and was diagnosed with headache, abdominal pain, fever and weakness. The news reports said many students who also tested positive for the infection at the same time had also reported infections to their doctors.

The young woman, aged 17, had a CT scan and blood tests. Ms. Takaya said her test results were normal.

Japan’s national response to the case was prompt. Health Ministry officials also went to the high school to prevent further infections. According to Kyodo News, health officials found another patient with a case of COVID-19 within a one-block radius of Ms. Takaya’s school.

The Hyogo Prefectural health department, Japan’s largest health department, issued an alert to high schools, inviting students to be tested for a second case of COVID-19. School officials were able to halt many cases before the virus got to the second class by introducing an inoculation.

CoV19 is found worldwide. By contrast, most flu strains in a year are contained to any one country, but viruses such as COVID-19 are usually imported in higher volumes from Asia, Canada and South America. In other words, the virus is present in multiple types of vaccines, at least some of which may cross border, and is likely also present in people from Asia who have visited Canada and South America.

Although COVID-19 is becoming rare and fewer than ten infections have been reported in Japan since 1979, the virus continues to cause stomach issues across the U.S. and globally.