A blog from the President Professor Gordon Dougan FRS on the hantavirus outbreak
I recently rushed back from a cruise across the Pacific to attend the Annual Microbiology Conference in Belfast. My wife and I took a flight from Honolulu, leaving on the Saturday and arriving safely in Belfast on Monday afternoon after spending a night in Seattle. During our cruise we visited many exotic islands and countries between Sydney and Honolulu. As the cruise progressed, we heard more and more people with coughs of different severity and, as microbiologists, we wondered what the cause might be. Was it Covid-19, Respiratory Syncytial virus or a bacteria like Bordetella pertussis that can cause persistent coughing in adults? At the time, we did not suspect Hantavirus.
The emergence of a Hantavirus outbreak on a small cruise ship sailing from Ushuaia in Argentina across the Atlantic has caught everyone by surprise. I also visited Ushuaia a couple of years ago on a cruise around Cape Horn. It sits on the Straights of Magellan and is a lovely temperate costal naval town. Many people on that cruise had been on various trips around South America before getting on board. Quite a mix of people clustered together and perhaps ideal for respiratory transmission.
Hantaviruses are a broad genus of viruses that are harboured by rodents, with specific viral species adapted to particular species of rodent. Consequently, the geographical distribution of Hantaviral species matches that of their rodent host. Some Hantaviruses can infect humans. Human Hantavirus infections were originally documented in the Korean war in the 1950s, particularly in areas close to the Hantan River, but it took some time to isolate the virus. A Korean scientist named Ho Wang Lee was the first to report the isolation of Hantaan virus in 1976 from the striped field mouse and link this virus to the human infectious disease known as Korean Haemorrhagic Fever. I have been regularly visiting South Korea for the past 25 years in my role as a Trustee for the International Vaccine Institute. In the early 2000s I used to stay in the faculty residencies of the Seoul National University and was invited to a meal one evening with four Korean scientists that included Ho Wang Lee. He was a very interactive and charming man who, like me, enjoyed single malt whiskey and we spent the evening sharing our interests. It was clear he was revered by his South Korean colleagues.
The dogma is that most Hantaviruses that infect humans are not readily transmitted between people. Interestingly, there have been reports of limited human to human spread involving infections from Hantaviruses from South America, so this data ties into the recent cruise ship outbreak. I have been listening to some commentators describing the outbreak as being of ‘limited risk’. This is true based on our past experiences with these viruses but all microbiologists reading this article will know that microbes evolve and the status quo between pathogen and host is not fixed. Hantaviruses have unusual three segmented genomes based on single stranded, negative-sense RNA. They have a significant molecular evolution rate in terms of the speed in which they accumulate mutations in their genome. Additionally, reports indicate that the segmented genome can undergo reassortment rather like Influenza viruses. To my mind there is always a risk of host adaptation when viruses and other pathogens replicate in humans. A sensible risk assessment is required based on scientific knowledge and these are currently being provided by agencies such as the World Health Organisation.
This outbreak emphasises the importance of strong basic science, excellent virology, operational high containment facilities, and global molecular surveillance networks. I feel there has been some complacency about this since the Covid-19 pandemic. The UK stepped up during Covid in terms of vaccine development, therapeutics linked to large scale clinical trials, and Covid sequencing driving the identification of variants (CoGUK). We need to maintain these scalable capabilities and the Microbiology Society has a role in canvassing for this type of infrastructure and the funding for it. The threat of future outbreaks and epidemics will persist in this globally connected world with an increasing compromised human population.
A final word. Many commentators have said that we do not have a vaccine for Hantaviruses. This is not strictly true. Ho Wang Lee developed a vaccine against the Korean species of Hantavirus based on formalin-inactivated whole virus. I believe this is still manufactured in South Korea and China but is not licensed in Europe or the USA. It is likely that this vaccine does not provide cross protection to other Hantaviruses. However, it does provide a route towards vaccine development. Thus, we need to put protective Hantavirus (and other outbreak) vaccines on the shelf ready for any future threat.
You can read the Hantaviridae profile in the Society’s Journal of General Virology:
ICTV Virus Taxonomy Profile: Hantaviridae 2024 | Microbiology Society
