There’s no question that another pandemic will strike, but no one knows when or which virus will be the cause. What we can determine with pretty good clarity is how ready we’ll be, how well we’re constructing obstacles to slow the path of emerging threats and how fast we’re learning lessons from painful experience.
As the final remaining passengers disembarked from the MV Hondius cruise ship, on which at least seven people were confirmed to have been infected with hantavirus traveled, the answers are becoming increasingly clear: We’re still leaving a lot to chance, crossing our fingers and hoping for the best.
Consider the history of the Andes strain of the hantavirus. According to a paper in The New England Journal of Medicine, in 2018, a hantavirus outbreak with this strain — the same strain linked to the Hondius cruise — began in Epuyén, Argentina. It started after one infected person attended a birthday party with about 100 guests. He had a fever and was feeling tired, and he left after about an hour and a half. Five people who were in the room — but not necessarily all even sitting right next to him — later sickened.
One of those five partygoers most likely went on to infect six more people, including his spouse, and died 16 days after he became ill. During his wake, 10 more people became infected, from the spouse. It was about then that the public health authorities, realizing how dangerous the situation was, started enforcing strict quarantine measures. That seems to be how it finally died out.
Yet in recent days, the World Health Organization has reassured the public that hantavirus can be transmitted only through “close and prolonged contact” and that, as a result, it is unlikely to spread widely among the population at large. “The one thing with this one is that it’s much harder to catch,” President Trump said on Monday, echoing W.H.O. and U.S. public health officials. “It seems like it is not easy to spread.”
We know fairly little about the Andes strain of the Hantavirus, with an estimated 3,000 human cases over three decades. How could that assertion about it not being easy to spread be true given what we know about the 2018 superspreading event?
I reached out to Gustavo Palacios, the senior author of the study about the Epuyén outbreak. He seemed as baffled by these pronouncements as I was. He told me that the paper he and his fellow researchers wrote used the phrase prolonged or close contact but he explained that, as they had written in their article, they didn’t mean solely physical or bodily contact. He told me that they believed that the virus spread via respiratory secretions. Looking at the same study, an airborne transmission expert, Linsey Marr, told CBC/Radio Canada that “it’s strongly suggestive that airborne transmission is happening.”
Dr. Palacios also said that he and his co-authors had calculated the median reproduction number of the Andes virus to be 2.1 — meaning that one sick person infected about two other people. That’s more than enough for sustained human transmission. That reproduction number is not much lower than the initial strain of SARS-CoV-2, the virus that causes Covid-19, as calculated in February and March of 2020, by the way, so I’m not feeling great about the reassurances from health officials that this will not become a pandemic. How do they know?
Dr. Palacios was also worried about the differences between the previous Andes strain outbreak setting and the current one. Containing an outbreak in a tiny isolated rural village in Patagonia, Argentina, during the dry season is a different prospect than containing one on a cruise ship with ocean humidity conditions or with people traveling onward in planes.
At the same time, authorities keep insisting that only symptomatic people can spread the virus. In Dr. Palacios’s study, the transmission events that the researchers could trace had indeed occurred while people were displaying symptoms. But he’s also said that 48 hours before the onset of symptoms should be considered a high-risk period as well. He told me that people’s viral loads rise before symptoms break out, so it’s reasonable to assume there is some risk earlier. Besides, with a single study done after the fact, he and his team hadn’t been able to pinpoint every exact moment that a person passed the virus to another — many unknowns remained from that outbreak.
The last twist was that his paper shows that the incubation period (the time between virus exposure and symptoms) can be as long as 40 days. Some people get sick more than a month after being exposed, which is an unusually long stretch of time. That’s a big deal because it makes managing the outbreak much more challenging.
On April 25, a Dutch cruise passenger took a flight from St. Helena to South Africa while ill, collapsed at the airport after arrival and died soon after. While W.H.O. officials have claimed the risk of spread during the flight or on the ship was low, that incident was just 17 days ago — if incubation can be as long as 40 days, there are 23 days before we’ll know if all her contacts are in the clear. As of Monday, South Africa’s health minister said that the authorities had identified 97 possible contacts in the country exposed to the hantavirus and that 90 of them had been reached and advised that they were being monitored. Based on South Africa’s guidelines, this meant asking people to perform daily temperature and symptom checks and to contact authorities immediately if they get sick. It’s unclear if everyone on the plane has been reached, and we can only hope this is sufficient.
Meanwhile, photographs of crew members while still on the ship show many of them hanging around together in a hallway while waiting to be interviewed by health authorities, covering their mouths and noses with only flimsy masks. In photos that have circulated, one person who had just left the ship can be seen on a bus, still clad in protective gear, but having removed their mask, seen dangling over one ear.
After the Covid pandemic, after the 2002 SARS epidemic, after the Epuyén hantavirus outbreak, we really have learned too little. One key lesson from both SARS and Covid was how much superspreading can play a role. Early on, many infected people spread the virus to few people, which generated comforting statistics on average. But when the circumstances aligned, it turned out that a single person could infect a large number of people all at once, setting off chains of transmission that were difficult to control.
We still don’t fully understand why some people superspread and others do not. But if it can happen once, as it did in Epuyén, it can happen again.
During a press conference last week, a W.H.O. official addressed people who had disembarked, asking them to present themselves to health care authorities if they were developing symptoms. W.H.O. officials also kept defining transmission as happening through close prolonged contact — intimate partners, household members. Encouragingly, over the weekend, the W.H.O. published new technical documents to clarify its definition of the type of contact that could cause the spread of hantavirus. It now includes “close proximity exposure” as well as “exposure in enclosed or shared spaces.”
But even these definitions still suffer from a lack of learning from the Covid experience, such as limiting exposure to being within about six feet for a cumulative period of more than 15 minutes. We know from the study of airborne transmission that that guidance may be too rigid and fail to capture the full risk profile of the virus. The Epuyén outbreak doesn’t seem to fit that framework. Still, I would say this is better than nothing, and much better than how slow things were in 2020 and onward. But these guideline changes were done too quietly.
How are people who may have been exposed supposed to protect themselves if they are not told of the modes of transmission and the stakes accurately and loudly, including when the definitions evolve? Public health officials, from the W.H.O. to U.S. officials, would be more helpful if they stopped constantly reassuring people about the likelihood of future events they can’t accurately calculate — like the odds of a pandemic occurring or how long this outbreak could last — and just told us more details about the things that matter: mode of transmission, lengthy period of incubation and the inevitable uncertainty of something for which there is little actual knowledge.
If we’re lucky, this hantavirus outbreak will peter out, or resemble the 2002 SARS outbreak: It dies out with the help of safety measures and because the virus doesn’t adapt fast enough. If we are unlucky? It should be unthinkable, but here we are. And this time Health Secretary Robert F. Kennedy Jr. will be in charge of the U.S. response.
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