90-Second Read: Hantavirus and tuberculosis cases: Should we be worried?

Recent news reports have highlighted several infectious diseases incidents, including three tuberculosis clusters in Singapore and a suspected Hantavirus outbreak on a cruise ship in the Atlantic Ocean. Hantavirus pulmonary syndrome is a lung disease seen in the outbreak on the Atlantic cruise ship. Thirteen cases across three clusters over three years is a localized public health concern, but it does not signal a wider outbreak and carries no pandemic potential. Here are responses to these cases by infectious disease experts from Duke-NUS Medical School, Singapore. According to Professor Ooi Eng Eong, Emerging Infectious Diseases Signature Research Program, Duke-NUS Medical School, Singapore, Hantaviruses are a group of viruses that are naturally found in rodents, including urban rats like the brown and black rats in Singapore.

After that initial discovery, many other Hantaviruses have been discovered in many different parts of the world, including Southeast Asia, Europe, and the Americas. Hantaviruses are shed from infected rodents in their excretions. Regardless of the type of Hantaviruses found in Singapore, the method to prevent such infections is rodent control, not only in residential and eating places but also in ports and shipyards where rodents from elsewhere could be inadvertently introduced into Singapore. When the droppings dry, Hantaviruses can become airborne and be accidentally inhaled by humans. Alternatively, Hantaviruses can also be transmitted from rodents to humans via contaminated food, rat bites, and scratches.

Infection can result in a wide range of symptoms and illnesses, from mild fever to hemorrhagic fever and renal syndrome (HFRS) and Hantavirus pulmonary syndrome. Likewise, some but not all Hantaviruses are also associated with severe human disease. Although Seoul Hantavirus can cause HFRS, the risk of such severe disease is low. There is neither a vaccine nor antiviral treatment for Hantavirus infection. They are so named because the first virus in this group was discovered as the cause of the Korean hemorrhagic fever epidemic among soldiers operating on the banks of the Hantan River during the Korean War.

There are many different Hantaviruses and their propensity to cause disease in humans are different. Research studies in Singapore have found Seoul Hantavirus antibodies in rodents, suggesting that this specific virus is present in Singapore. Most infections, unlike the more virulent Hantaan virus and Sin Nombre virus, would either be asymptomatic or only present as flu-like febrile illness. Assistant Professor Shurendar Selva Kumar, Center for Outbreak Preparedness, Duke-NUS Medical School, Singapore, said that what is being observed in Bedok Central is not a sudden resurgence of tuberculosis, but a reflection of Singapore's advanced detection capabilities. Transmission requires prolonged contact with an infectious individual—not incidental exposure—and all patients identified have been promptly treated and are currently non-infectious.