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Health officials in Hong Kong reported the cause of a local case of Japanese encephalitis (JE) affecting a male patient who stayed in Grantham Hospital in the entire incubation period–a blood transfusion given while hospitalized.

Donated blood /Ethan Morgan USAF
Donated blood /Ethan Morgan USAF

The patient aged 52 was admitted to Queen Mary Hospital on May 10 for organ transplant for his underlying illness. He had fever and decreased consciousness on July 6 after receiving blood transfusion in Grantham Hospital, followed by acute confusion and myoclonus on July 8. He developed seizures in unconscious condition on July 9. He was transferred to the Intensive Care Unit of Queen Mary Hospital for further management on July 14. He is now in critical condition.

His cerebrospinal fluid (CSF) and serum sample tested positive for immunoglobulin M (IgM) antibodies against JE upon laboratory testing. His CSF also tested positive for JE virus.

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Residual samples of the blood transfused to the patient in the incubation period were retrieved for laboratory investigations. Upon the Hong Kong Centre for Health Protection (CHP) testing, one blood sample from Queen Mary Hospital (QMH) and one from the Hong Kong Red Cross Blood Transfusion Service tested positive for JE virus, both originating from the same donation which was transfused to the patient on June 22. Of note, the genetic sequence of the virus from the positive sample from QMH was identical to that of the patient. Samples from three other donations transfused to the patient on different dates tested negative.

The CHP has swiftly conducted source tracing and identified the 46-year-old male blood donor concerned who gave blood on May 29. He has been asymptomatic all along.

Contact tracing has identified two other patients who had received the donor’s blood products. One is a discharged patient of QMH who received transfusion on June 2 and QMH is contacting the patient for clinical assessment and blood testing. The other is a patient of Queen Elizabeth Hospital who died of chronic illness on July 4 after surgery, during which the patient received transfusion on June 20. Relatives will be contacted.

Epidemiologically, the donor had no travel history to JE-endemic areas and his home contact has remained asymptomatic. He lives in Kingswood Villas, Tin Shui Wai and recalled no mosquito bites.

“The CHP will proceed standard public health actions as a precautionary measure. The Food and Environmental Hygiene Department (FEHD) and the Agriculture, Fisheries and Conservation Department have been informed for necessary follow-up,” Controller of the CHP, Dr Wong Ka-hing said.

Japanese encephalitis (JE) is the most important cause of viral encephalitis in Asia. About 68,000 clinical cases are reported annually. It usually occurs in rural or agricultural areas, often associated with rice farming.

LISTEN: Dr Anna Lena Lopez, a pediatric infectious disease specialist and research associate professor at the University of the Philippines in Manila discusses JE and the vaccine

JE virus is transmitted to humans through the bite of infected Culex species mosquitoes, particularly Culex tritaeniorhynchus.

While JE is principally mosquito-borne, scientific literature show that, based on nature of similar flaviviruses, blood transfusion and organ transplant are considered to be potential modes of transmission of JE virus.

Most JE virus infections are mild (fever and headache) or without apparent symptoms, but approximately 1 in 250 infections results in severe disease characterized by rapid onset of high fever, headache, neck stiffness, disorientation, coma, seizures, spastic paralysis and death. The case-fatality rate can be as high as 30% among those with disease symptoms.

There is a protective vaccine against Japanese encephalitis virus.