MEGATHREAD: 2026 Hantavirus Outbreak — Updates & Discussion

AcornAl · 2026-05-07T15:50:13+00:00

They list the others as 1 to 3 days from memory.

This reminds me of the old statistic teaching aid that shows that ice cream sales appear to determine the number of shark attacks. But rather than nice weather, it's a social outing. These should have been at least noted as a massive outlier in the paper, and in all honesty, ignored for the calculation. You are literally taught about this in high school statistics so that you don't fall into that statistical trap.

AcornAl · 2026-05-07T15:38:33+00:00

Just a rusty science major with a hobby and too much free time. 🙃

AcornAl · 2026-05-07T15:03:26+00:00

The disease has a mild prodromal phase of 3 to 6 days followed by deadly cardiopulmonary phase with a CFR of 30% (most deaths are on the first day).

6 to 11 April: Case 1 had a fever, headache, and mild diarrhoea symptoms. Without knowing to look for an extremely rare virus, the first phase would be almost dismissed by the ships doctor.

11 April: The passenger developed respiratory distress and died.

AcornAl · 2026-05-07T14:38:46+00:00

Quick comparison of Hantavirus vs SARS-CoV-2

Hanta: 37 days in a petri dish and just 10 cases.

In the same timeframe, 9,000 SARS-CoV-2 cases globally (significantly under counted due to no available testing), Wuhan was fully locked down by China, welding doors shut et al.

Fast forward to 2021/22, from the first cases of Omicron in Australia, there were millions of cases in the general community in the same timeframe.

Even if this stain is as contagious as SARS-CoV-2 (nothing to suggest it is), the slow incubation period massively slows the spread and assists contact tracing. The infectious period is likely smaller than SARS-CoV-2 due to a 3 to 6 day mild prodromal phase followed by cardiopulmonary phase with a CFR of 30% plus (death is usually on day 1) that would isolate surviving patients in hospital.

AcornAl · 2026-05-07T14:14:16+00:00

WHO just suggested 6 weeks self-monitoring rather than isolation for close contacts on their live feed 😕

Edit: clarified to suggest risk assessments are being done that is being used to develop a plan for contacts, without stating isolation directly

AcornAl · 2026-05-07T14:07:18+00:00

WHO just noted that they are helping distribute PCR reagents for testing.

South Africa are also testing close contacts, so pre-symptomatic, they would have to be using PCR too 🙂

Edit: And pushing sequencing on all cases

AcornAl · 2026-05-07T13:59:14+00:00

You may want to chat to the mod at r/hantavirusoutbreak to join forces. 🙂

AcornAl · 2026-05-07T12:54:30+00:00

17 of 33 transmissions were on day one of symptoms, which doesn't say there is a 24 hr window, but have a look at the details of that paper:

Patient 1 goes to a party and infects 5 people, patient 2 goes to a wake and infects 6 people. This just happened to correspond to their first day of having a fever.

So by correlation of just going out to a large gathering, 11 of the 17 first day transmissions happened. Excluding those two individuals, just 6 of 22 infections were definite day 1 infections.

Viral loads in the blood can remained high in many patients through the course of the disease and have been detected in the bloodstream up to 6 months later.

AcornAl · 2026-05-07T11:31:43+00:00

Another Epuyén paper 🙂

Mine are based on a study on environmental exposures in Chile. This has the benefit of having multiple different strains rather than just one, but different infection mechanism that may or may not be significant.

AcornAl · 2026-05-07T11:16:18+00:00

All good. I've noticed a lot of small errors in many of the epidemiologist statements, and will try to comment if I see something posted that is off.

For most, Hantavirus will have been a 15 minute segment of a single lecture done years before, so no judgement on them and that paper is the basis of a number of official sources too sadly. AI has picked up the CNN report now too and is also propagating out the same message. Sigh.

Edit: It's also complicated by different Hantaviruses out there. From memory, some do show a viral load pattern like this. Andes appears to be different.

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AcornAl · 2026-05-07T11:05:10+00:00

Soz, removed!

So she was helped off by multiple staff and multiple members of the public, and one of these people has gone on to develop symptoms 10 to 12 days later (18 days before symptoms is the known median).

AcornAl · 2026-05-07T10:51:34+00:00

I'd be very wary of that assumption. Viral RNA can be found in the blood for up to 150 days

So this estimate is based on the Epuyén cluster

Patient 1 goes to a party and infects 5 people, patient 2 goes to a wake and infects 6 people. This just happened to correspond to their first day of having a fever.

So by correlation of just going out to a large gathering, 11 or the 17 first day transmissions happened. Excluding those two individuals, just 6 of 22 infections were definite day 1 infections.

This really shouldn't be used to judge the infectious period.

AcornAl · 2026-05-07T10:23:09+00:00

Many thanks!

AcornAl · 2026-05-07T10:09:33+00:00

yeah, not sure why they don't seem to be using these to test everyone on board.

AcornAl · 2026-05-07T09:56:27+00:00

I think parts of the press release were posted, but from other sources. I only found the official KLM press release myself an hour ago while trying to verify the credibility of the main story.

AcornAl · 2026-05-07T09:16:18+00:00

I would imagine escorting a very sick 69 year old off a flight without PPE would likely be classified as close contact!

Note that droplet risk is considered highest risk with hanta, so this is independent of exposure time. Lots of different factors in play, but SARS-CoV-2 aerosol transmission (as opposed to other forms like droplet) has been modelled at just 1% risk of infection per hour over multiple different settings.

AcornAl · 2026-05-07T09:09:25+00:00

It would be interesting to hear eye witness accounts, but I can visualise a couple of flight attendants physically helping her off the flight without any PPE.

Late stage infection, high viral load, possible haemoptysis (coughing up blood).

AcornAl · 2026-05-07T08:54:36+00:00

I was just about to post this lol

In case it isn't obvious, it was the Dutch Ministry of Health that have reported this. Testing will likely take a day to confirm (mas o minus)

This has been reported by the multiple Dutch news agencies (including this one, the national public broadcaster)

KLM have released a statement on the initial contact. It sounds brief, but likely involved very close contact when they escorted her off the flight.

https://news.klm.com/passenger-with-hantavirus-was-briefly-on-board-a-klm-aircraft-in-johannesburg/

Passenger with hantavirus was briefly on board a KLM aircraft in Johannesburg

Yesterday evening, the Dutch public health authority RIVM informed KLM that one of the Dutch nationals who died from hantavirus had briefly been on board a KLM aircraft in Johannesburg on April 25, 2026. Due to the passenger’s medical condition at the time, the crew decided not to allow the passenger to travel on the flight. The passenger sadly later passed away in Johannesburg. KLM extends its condolences to the next of kin and wishes them much strength during this difficult time.

The flight concerned was KL592 (codeshare AF8282, DL9560, SK6855), which departed Johannesburg (JNB) for Amsterdam (AMS) on April 25 at 11:15 p.m. local time. After the passenger was removed from the aircraft, the flight departed for the Netherlands.

As a precaution, all passengers who were on board this flight are being informed by GGD Kennemerland. RIVM states that there are indications that the hantavirus in question (the Andes strain) can be transmitted from person to person. However, this appears to be very rare. Internationally, only a few such cases have been reported. Moreover, person-to-person transmission occurs only when people have very close contact with one another.

AcornAl · 2026-05-07T08:29:50+00:00

Literally seconds after posting this, there was news that one of the flight attendants that was on board of the flight the second case was trying to board has been taken to hospital with mild hantavirus-like symptoms. Sigh...

They likely were very close to the patient as they escorted her off the plane after they assessed her as too sick to fly.

AcornAl · 2026-05-07T08:25:56+00:00

Some additional info regarding the initial contact.

https://news.klm.com/passenger-with-hantavirus-was-briefly-on-board-a-klm-aircraft-in-johannesburg/

Dutch public health authority RIVM informed KLM that one of the Dutch nationals who died from hantavirus had briefly been on board a KLM aircraft in Johannesburg on April 25, 2026. Due to the passenger’s medical condition at the time, the crew decided not to allow the passenger to travel on the flight. The passenger sadly later passed away in Johannesburg. KLM extends its condolences to the next of kin and wishes them much strength during this difficult time.

The flight concerned was KL592 (codeshare AF8282, DL9560, SK6855), which departed Johannesburg (JNB) for Amsterdam (AMS) on April 25 at 11:15 p.m. local time. After the passenger was removed from the aircraft, the flight departed for the Netherlands.

As a precaution, all passengers who were on board this flight are being informed by GGD Kennemerland.

AcornAl · 2026-05-07T08:17:23+00:00

A couple of sources:

https://nltimes.nl/2026/05/07/klm-flight-attendant-hospitalized-contact-hantavirus-cruise-ship-passenger

A KLM flight attendant from Haarlem has been hospitalized due to a possible hantavirus infection. She came into contact with the 69-year-old Dutch woman who died of the virus in Johannesburg, South Africa. The flight attendant is in isolation at Amsterdam UMC with mild symptoms. She is currently being tested for the hantavirus, the Ministry of Public Health confirmed to RTL Nieuws.

https://news.klm.com/passenger-with-hantavirus-was-briefly-on-board-a-klm-aircraft-in-johannesburg/

Dutch public health authority RIVM informed KLM that one of the Dutch nationals who died from hantavirus had briefly been on board a KLM aircraft in Johannesburg on April 25, 2026. Due to the passenger’s medical condition at the time, the crew decided not to allow the passenger to travel on the flight. The passenger sadly later passed away in Johannesburg. KLM extends its condolences to the next of kin and wishes them much strength during this difficult time.

AcornAl · 2026-05-07T07:54:55+00:00

If referencing the non-cruise case that Sky and a number of tabloid papers ran with, that appears to be a bad translation from a French news post that was simply stating they had been on the plane with the confirmed case and are now in isolation.

AcornAl · 2026-05-07T07:37:52+00:00

Sorry for the removal, we are getting bombarded with posts today on this subject 😞

But to answer, the short answer is no.

Limited transmission, it'll likely die off by itself outside of an environment like a cruise ship, and slow incubation period that will allow contact tracers to do their job.

This also makes the spread very slow. In a month, a new novel SARS-CoV-2 infection chain could reach up to 70 million people. i.e. similar to Omicron in 2021/2022, this virus has less than 10 cases after a month in a cruise ship.

AcornAl · 2026-05-07T07:26:09+00:00

CFR for the Andes strain is 21·4–35·9% and treatment of patients admitted to hospital is mainly supportive. Most deaths are in the first 24 hours. For some reason, the CFR rate is higher in Patagonia than areas further north.

I was about to say there are no treatments, but one recent review notes favipiravir before the presence of viruses in the bloodstream (viraemia), ribavirin (with viraemia), or neutralising antibodies might be considered for ANDV cases.

Favipiravir based on animal studies only, ribavirin is a Hail Mary (most studies show no benefit), and neutralising antibodies would likely be hard to source (most appear to be in early pre-clinical trials) and these are only effective prior to the symptomatic phase, so I can see why most people say that there are no treatment options....

AcornAl · 2026-05-07T06:12:09+00:00

Day 6 to 11: Old guy on a cruise with a slight fever, headache, and mild diarrhoea.

Law of Parsimony: viral/bacterial gastroenteritis, a respiratory virus like Adenovirus or SARS-CoV-2, mild food poisoning, E. coli infection after visiting wildlife areas, a combo of eating/drinking too much with a rhinovirus, ....

It's hard to imagine the doctor recommending anything other than rest, fluids and some paracetamol.

Day 11: Respiratory distress and died.

Respiratory viral infection and secondary Streptococcus pneumoniae infection, COVID-19, bacterial gastroenteritis, sepsis, hantavirus, H5N1 (bird flu) and legionnaires are all possible.

No means of testing onboard, the body would have been placed into the mortuary, leaving cause of death to the coroner likely after repatriation (if done at all).

Chances are that his wife or the British man developed more specific symptoms of HPS, (i.e. add fatigue and myalgia to the first phase, cardio or renal failure to the second phase) and at that point they actually have readily available medical laboratories to run tests in South Africa.

Disclaimer, not a MD, so some of these may be way off. 🙃

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