Alex Azar, speaking in Uganda, told reporters that he and others are "very concerned" and urged Tanzania's government to share laboratory results regarding the case. The Ebola outbreak in neighboring Congo has become the second-deadliest in history, with confirmed cases now exceeding 3,000.
Azar said efforts were underway to secure Tanzania's compliance with international health regulations and obligations to the World Health Organization "to protect Tanzanians as well as all people in the region."
Tanzania's government said Saturday there is no confirmed case of Ebola in the East African nation. No confirmed Ebola case has ever been recorded there.
WHO in a statement last week noted a rumor regarding a death in Tanzania from an unknown illness and said it was sending a technical team to investigate "as a matter of urgency."
According to an internal WHO document seen by The Associated Press, the patient, a 34-year-old woman, died on Sept. 8 and was buried that day. It was not clear where she died.
The document says the victim most recently was a student in central Uganda, where she visited health facilities on a research mission, before returning to Tanzania on Aug. 22.
No case of Ebola has been reported in Uganda's central region.
"This mysterious disease has to be investigated and samples have to be tested. We couldn't rule out any of the viral hemorrhagic fevers and the investigation will continue," Dr. Yonas Woldemariam, the WHO representative in Uganda, said Monday.
The Ebola outbreak in eastern Congo, which was declared over a year ago, has killed nearly 2,000 people. Health workers have been challenged by community mistrust and insecurity caused by years of rebel attacks.
Cases of Ebola patients crossing borders during this outbreak have been rare.
In June, a family of Congolese with sick family members crossed into Uganda via a bush path. Two died of Ebola inside Uganda. And in August, a Congolese girl tested positive for Ebola and later died in Uganda after traveling from Congo.
Follow Africa news at https://twitter.com/AP_Africa
Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.