The man developed the disease after undergoing a liver transplant following chronic infection with hepatitis B. He continued to show signs of abnormal liver function, said Sridhar, with no obvious cause.
The report said that the victim was 56-year-old man in may last year, transplanted the liver.
The world's first human case of rat disease has been diagnosed in China.
Rodent problems have worsened in Hong Kong with experts saying they found signs of rat infestation near his home, and suspected he had consumed something that had been in touch with rat faeces.
Rat hepatitis E virus is very distantly related to human hepatitis E virus variants, the researchers say.
Sridhar said, "The patient is cured, as of this stage we can no longer detect the virus in any clinical specimen".
"We postulate that contamination of food by infected rat droppings in the food supply is possible", the researchers said.
Humans tend to be infected by ingesting infected faecal matter, such as drinking contaminated water or through contact with poor sanitation.
But, as of May 2018, there was not a US Centers for Disease Control and Prevention (CDC) approved hepatitis E vaccine.
It can not be spread through sex or sharing needles like other forms of the virus, but has been caught from blood transfusions and organ transplants in the past.
Previous year researchers from Oxford University first demonstrated that hepatitis B virus is associated with an increased risk of Parkinson's disease.
Many people clearly have hepatitis, based on their symptoms, but they test negative on all the human strains known to exist, Adalja said.
The man is now recovering after being treated in hospital, the Morning Post added.
Symptoms of hepatitis E in humans include fever, fatigue, nausea and vomiting, jaundice, abdominal pain, joint pain and dark-colored urine.
A sustained period of hot and humid weather has caused rodent problems in Hong Kong to escalate, multiple sources reported. It is a liver disease that affects 20 million people globally each year, according to the World Health Organization.
Hepatitis E is a major health threat in developing countries in Africa and Asia and in the past has been contracted from eating undercooked pork and deer meat.