(CNN) The father and sister of a Missouri woman who tested positive for novel coronavirus disregarded a quarantine and went to a school function on Saturday.

The patient, who is in her 20s, reported feeling sick after returning from Italy on March 2. She contacted a coronavirus hotline three days later, on Thursday, and spoke with health officials who advised her to get tested, St. Louis County Executive Sam Page said.

The patient's family had been advised to self-quarantine at their home in Ladue as they awaited test results, Page said.

The family was informed that the woman was Missouri's first presumptive positive case on Saturday.

That night the patient's father defied instructions to stay at home and went to a school function with another daughter, Page said.

"The way the family has reacted to this situation is really a tale of two reactions," Page said. "And a study of how people should and should not react to the coronavirus."

Page lauded the patient, saying she has "conducted herself responsibly and maturely " and she has been "complying with the health departments instructions."

"The patient's father did not act consistently with the health department's instructions," Page told reporters Sunday. "Instead, last night he decided to take his other daughter to a school function."

Page said health and county officials learned about the father's actions Sunday and told him that he needs to stay in isolation. If he does not comply with orders, health officials will seek a court order and "issue a formal quarantine that will require him and the rest of his family to stay in their home by the force of law," Page warned.

The family has been told numerous times that self quarantine is necessary as health officials continue to investigate the woman's case, Page said.

"We depend on common sense and goodwill of the people that we communicate with and when we ask someone to quarantine and they tell us they will we have to trust that," Page said.