I ran through my checklist. Looks low-risk to me. Basically a very deadly disease that nevertheless shows nil or inefficient human-to-human transmission and doesn’t show signs of regional or global growth. It depends heavily on specific South American rat species for transmission to humans. The original exposure was on or around April 1. There are no new concerning mutations (see below), and so far the flight attendant who had been feared to have picked it up on a flight has tested negative, though there’s an up to 6 week incubation period and she was exposed on April 25th, about 2 weeks ago. There were also 3 other plane passengers who had contact with an infected person on a plane and they’ve tested negative so far as well.
The consensus public health position is that “person-to-person transmission is possible through close personal contact, such as between couples.” If it turns out that this is wrong and that it’s much more human-transmissible than previously believed, then the complete failure to quarantine passengers after the discovery of hantavirus on the Hondius cruise ship and first passenger death would completely alter my projection. But so far, there do not seem to be signs of that.
Getting on a evolutionary biology level, if Andes virus were to become efficiently human-transmissible, the last place I’d expect to see it enter the human population is via tourists picking it up while bird watching in a garbage dump. That’s a setting where the human-rodent interface is minimal. In that setting, there’s little selection pressure on the virus to jump to humans and transmit efficiently. In a hypothetical Andes virus pandemic, I’d strongly have expected patient 0 to be a Chilean or Argentinian villager living in conditions that sadly expose them to routine contact with rats. I’d expect the outbreak to spread first in a local village, not on a luxury cruise ship.
Instead, it looks to me like a couple of tourists made the risky and unusual decision to put themselves in a uniquely rodent-infested location without protection, where they likely had the misfortune to inhale a large quantity of virus-infested aerosolized rat droppings. Then they got into the close quarters of a cruise ship, which completely failed to execute the measures it should have taken to address their illness, including a failure to quarantine. This allowed limited spread to other close-quarters passengers, exactly as we have observed this virus to be capable of in the past. This, combined with the lack of new mutations, suggests we’re dealing with exposure to a known-quantity, transmission-inefficient virus in a demographic that doesn’t usually get exposed.
The concern is due to the fact that those passengers had travelled internationally by the time quarantining and contact tracing was initiated, combined with the deadliness of the virus. But it takes a combination of spread in international populations and transmissibility and deadliness and lack of treatment to make a pandemic, and currently we only appear to have deadliness and lack of treatment. The only reason it even gets 4 points is probably because it’s so rare and such a disease of poverty that big pharma’s never invested in a vaccine or treatment. The main scary thing, like ebola, is the very high CFR. But that is not the grounds for a global pandemic. It’s just a tragedy for a few hundred people a year.
Is there an efficient transmission route, such as respiratory droplets, airborne transmission or via the bites of common jumping or flying insects?
“Hantaviruses are transmitted mainly through aerosols and droplets that contain rodent excretions, as well as through contaminated food, bites, and scratches.”—Wikipedia.
Incubation time is up to 6 weeks.
Possibly. There are cases of human-to-human transmission, but this is contested. The Argentine government thinks the original two cruise ship cases contracted it while bird watching at a garbage dump, but several other passengers on the cruise ship were sickened.
Update 5/8/2026:flight attendant tests negative, but result inconclusive due to 6-week incubation period. No new concerning mutations. source
“On Thursday evening, Tedros Ghebreyesus, the director-general of the World Health Organization, said in a message that the flight attendant, who has been reported to have symptoms, had tested negative on two tests.… Mr. Ghebreyesus did caution, however, that the virus can have a long incubation time.”
For context, a Hondius cruise linear passenger, very sick with what turned out to be hantavirus, got on a plane. The passenger was handled on that plane by a flight attendant. The sick passenger was removed from the flight before takeoff due to her illness and later died. The flight attendant has been hospitalized and tested for hantavirus. I haven’t found a clear report of whether the flight attendant was sick or not. The flight attendant’s test results have been negative so far, but the incubation time is up to 6 weeks.
“Genetic sequencing of samples in South Africa suggests that the virus is nearly identical to the version seen in Argentina and has not mutated in ways that would make it a greater threat, according to Tulio de Oliveira, director of the Centre for Epidemic Response and Innovation at Stellenbosch University in South Africa. Dr. De Oliveira was not involved in the work but said the results had been presented to an expert group of which he is a member.”
Graded as a “no” as even if human-to-human transmission is possible, it currently appears to be inefficient and still heavily depend on rats.
Does it seem to spread rapidly within affected communities, going from a few cases to a major local emergency within a month? If R0 has been credibly estimated, is the mean of the range higher than 1?
No. This appears to be a sporatic, locally contained, chronic issue. “More than a hundred cases of HPS caused by Andes virus occur each year, most of them in Argentina and Chile.”—Wikipedia
Has it achieved community spread in non-endemic countries on at least 3 continents, and in a set of countries comprising both 15% of world population and 15% of world GDP?
No.
Is screening for the causative agent difficult due to test unavailability/unreliability/slowness, vector-based transmission, or transmissibility that is highest in early/asymptomatic stages? If the causative agent is unknown, mark “unknown.”
No. “ANDV infection is diagnosed based on observation of symptoms and testing for hantavirus nucleic acid, proteins, or hantavirus-specific antibodies.”—Wikipedia
Danger: case fatality rates, overwhelm, economic impacts, treatment
If a credible case fatality rate has been estimated, is it 1% or higher? Alternatively, is the number of deaths divided by the number of confirmed cases being reported at around 5% or higher in at least 3 countries with reliable data?
Yes. The case fatality rate from infection is high, at about 40%.
Is there a concern about hospital overwhelm or medical supply shortages in industrialized nations?
No.
Does the disease heavily affect career-age people (age 25-65), or frequently leave survivors with lasting disability?
Yes (tentative)
Is there no clearly effective treatment?
Yes, there is no clearly effective treatment. “Treatment is supportive in nature and includes supplementing oxygen during the cardiopulmonary phase.”
Spread limitations: demographics, geography
If some non-age-related demographics are heavily affected and others are not, do the heavily affected demographics amount to 15% or more of the population? If almost the whole population is about equally affected, mark “yes.”
Yes (tentative)
Is the disease potentially transmissible across most of the world population (i.e. does not work via a vector that has a geographically limited range)? If the causative agent is unknown, mark “unknown.”
No. Reports of human-to-human transmission are rare and contested. It appears to heavily depend on the particular rat species that transmit it.
Social effects: communications, shutdown, research, deaths
Has the disease made front page news on at least 3 different days in the New York Times, and also received the WHO designation “public health emergency of international concern” or the equivalent?
No.
Has there been a quarantine of a city with over 1 million inhabitants? In a country comprising at least 5% of world population or GDP, has there been a cancellation of major public events, or travel restrictions on passengers arriving from or via this country?
No.
Has the pharmaceutical industry begun a widespread research effort to produce a novel treatment or novel vaccine, and/or has industry begun a major emergency effort to build physical infrastructure or equipment (hospitals, ventilators, etc)?
I ran through my checklist. Looks low-risk to me. Basically a very deadly disease that nevertheless shows nil or inefficient human-to-human transmission and doesn’t show signs of regional or global growth. It depends heavily on specific South American rat species for transmission to humans. The original exposure was on or around April 1. There are no new concerning mutations (see below), and so far the flight attendant who had been feared to have picked it up on a flight has tested negative, though there’s an up to 6 week incubation period and she was exposed on April 25th, about 2 weeks ago. There were also 3 other plane passengers who had contact with an infected person on a plane and they’ve tested negative so far as well.
The consensus public health position is that “person-to-person transmission is possible through close personal contact, such as between couples.” If it turns out that this is wrong and that it’s much more human-transmissible than previously believed, then the complete failure to quarantine passengers after the discovery of hantavirus on the Hondius cruise ship and first passenger death would completely alter my projection. But so far, there do not seem to be signs of that.
Getting on a evolutionary biology level, if Andes virus were to become efficiently human-transmissible, the last place I’d expect to see it enter the human population is via tourists picking it up while bird watching in a garbage dump. That’s a setting where the human-rodent interface is minimal. In that setting, there’s little selection pressure on the virus to jump to humans and transmit efficiently. In a hypothetical Andes virus pandemic, I’d strongly have expected patient 0 to be a Chilean or Argentinian villager living in conditions that sadly expose them to routine contact with rats. I’d expect the outbreak to spread first in a local village, not on a luxury cruise ship.
Instead, it looks to me like a couple of tourists made the risky and unusual decision to put themselves in a uniquely rodent-infested location without protection, where they likely had the misfortune to inhale a large quantity of virus-infested aerosolized rat droppings. Then they got into the close quarters of a cruise ship, which completely failed to execute the measures it should have taken to address their illness, including a failure to quarantine. This allowed limited spread to other close-quarters passengers, exactly as we have observed this virus to be capable of in the past. This, combined with the lack of new mutations, suggests we’re dealing with exposure to a known-quantity, transmission-inefficient virus in a demographic that doesn’t usually get exposed.
The concern is due to the fact that those passengers had travelled internationally by the time quarantining and contact tracing was initiated, combined with the deadliness of the virus. But it takes a combination of spread in international populations and transmissibility and deadliness and lack of treatment to make a pandemic, and currently we only appear to have deadliness and lack of treatment. The only reason it even gets 4 points is probably because it’s so rare and such a disease of poverty that big pharma’s never invested in a vaccine or treatment. The main scary thing, like ebola, is the very high CFR. But that is not the grounds for a global pandemic. It’s just a tragedy for a few hundred people a year.
THE CHECKLIST
Version: 0.2.4
Current score: 4/14
Last updated: 8 May 2026
Transmissibility: efficiency, intra-community spread, inter-community spread, outside view
Is there an efficient transmission route, such as respiratory droplets, airborne transmission or via the bites of common jumping or flying insects?
“Hantaviruses are transmitted mainly through aerosols and droplets that contain rodent excretions, as well as through contaminated food, bites, and scratches.”—Wikipedia.
Incubation time is up to 6 weeks.
Possibly. There are cases of human-to-human transmission, but this is contested. The Argentine government thinks the original two cruise ship cases contracted it while bird watching at a garbage dump, but several other passengers on the cruise ship were sickened.
Update 5/8/2026: flight attendant tests negative, but result inconclusive due to 6-week incubation period. No new concerning mutations. source
“On Thursday evening, Tedros Ghebreyesus, the director-general of the World Health Organization, said in a message that the flight attendant, who has been reported to have symptoms, had tested negative on two tests.… Mr. Ghebreyesus did caution, however, that the virus can have a long incubation time.”
For context, a Hondius cruise linear passenger, very sick with what turned out to be hantavirus, got on a plane. The passenger was handled on that plane by a flight attendant. The sick passenger was removed from the flight before takeoff due to her illness and later died. The flight attendant has been hospitalized and tested for hantavirus. I haven’t found a clear report of whether the flight attendant was sick or not. The flight attendant’s test results have been negative so far, but the incubation time is up to 6 weeks.
“Genetic sequencing of samples in South Africa suggests that the virus is nearly identical to the version seen in Argentina and has not mutated in ways that would make it a greater threat, according to Tulio de Oliveira, director of the Centre for Epidemic Response and Innovation at Stellenbosch University in South Africa. Dr. De Oliveira was not involved in the work but said the results had been presented to an expert group of which he is a member.”
Graded as a “no” as even if human-to-human transmission is possible, it currently appears to be inefficient and still heavily depend on rats.
Does it seem to spread rapidly within affected communities, going from a few cases to a major local emergency within a month? If R0 has been credibly estimated, is the mean of the range higher than 1?
No. This appears to be a sporatic, locally contained, chronic issue. “More than a hundred cases of HPS caused by Andes virus occur each year, most of them in Argentina and Chile.”—Wikipedia
Has it achieved community spread in non-endemic countries on at least 3 continents, and in a set of countries comprising both 15% of world population and 15% of world GDP?
No.
Is screening for the causative agent difficult due to test unavailability/unreliability/slowness, vector-based transmission, or transmissibility that is highest in early/asymptomatic stages? If the causative agent is unknown, mark “unknown.”
No. “ANDV infection is diagnosed based on observation of symptoms and testing for hantavirus nucleic acid, proteins, or hantavirus-specific antibodies.”—Wikipedia
Danger: case fatality rates, overwhelm, economic impacts, treatment
If a credible case fatality rate has been estimated, is it 1% or higher? Alternatively, is the number of deaths divided by the number of confirmed cases being reported at around 5% or higher in at least 3 countries with reliable data?
Yes. The case fatality rate from infection is high, at about 40%.
Is there a concern about hospital overwhelm or medical supply shortages in industrialized nations?
No.
Does the disease heavily affect career-age people (age 25-65), or frequently leave survivors with lasting disability?
Yes (tentative)
Is there no clearly effective treatment?
Yes, there is no clearly effective treatment. “Treatment is supportive in nature and includes supplementing oxygen during the cardiopulmonary phase.”
Spread limitations: demographics, geography
If some non-age-related demographics are heavily affected and others are not, do the heavily affected demographics amount to 15% or more of the population? If almost the whole population is about equally affected, mark “yes.”
Yes (tentative)
Is the disease potentially transmissible across most of the world population (i.e. does not work via a vector that has a geographically limited range)? If the causative agent is unknown, mark “unknown.”
No. Reports of human-to-human transmission are rare and contested. It appears to heavily depend on the particular rat species that transmit it.
Social effects: communications, shutdown, research, deaths
Has the disease made front page news on at least 3 different days in the New York Times, and also received the WHO designation “public health emergency of international concern” or the equivalent?
No.
Has there been a quarantine of a city with over 1 million inhabitants? In a country comprising at least 5% of world population or GDP, has there been a cancellation of major public events, or travel restrictions on passengers arriving from or via this country?
No.
Has the pharmaceutical industry begun a widespread research effort to produce a novel treatment or novel vaccine, and/or has industry begun a major emergency effort to build physical infrastructure or equipment (hospitals, ventilators, etc)?
No.
Have the death toll reached at least 2,000?
No.