What would cause a world wide pandemic?

Question

I am writing a story about being "alone" on earth, I want it to be caused by a virus but I am unsure about the details of it.

I know that the virus:

• Should kill most of the worlds population leaving a few people to restart life.
• Must have a herbal cure/vaccine so that the protagonist can meet someone.
• Must spread all over the world at a speed that the news and governments don't have enough time to fully report the problem.

My first thoughts for this virus is that it could be biological leading to an encounter between the protagonist and the antagonist.

It could be waterborne but then I wouldn't know what to do with the need to drink liquid.

I know I don't want a nuclear disaster to go off as I want the world to still be "inhabitable" after the outbreak.

EDIT/CONCLUSION:

I have combined the current answers and my own thinking. Since the protagonist is a software developer who has his own life like AI.

1. What if the world/humans relied on technology? like that movie called Wall E where the humans all got fat and needed technology to make them move. What if the Protagonists AI was an evil mastermind.

OR

2. What if humans wanted to spend more time with their families and go on holiday more? that boring jobs like nuclear waste management and repairing dangerous buildings were done by robots instead of humans.

Answer 1

Should kill most of the worlds population leaving a few people to restart life.

That's easy enough. As the author, you can simply declare this to be so.

Must have a herbal cure/vaccine so that the protagonist can meet someone.

A "herbal vaccine" isn't a thing; vaccines are made from weakened, inactivated or dismantled infection particles. They are also generally the end-product of a fairly sophisticated research and industrial process, so if one did exist for your virus it would have to have been made before the outbreak. There's a conspiracy hook for you.

A naturally occuring herbal cure also sounds slightly dubious, because the timescales involved make it largely impractical to discover in time to help anyone. If it had been discovered before, you've got another nice conspiracy hook. It might also facilitate the presence of groups of survivors who were already familiar with the herb and had been cultivating it for other uses (medicinal, recreational, agricultural, whatever).

Must spread all over the world at a speed that the news and governments don't have enough time to fully report the problem.

You'll have a real problem with this. You can get realtime news updates from anywhere in the world if you have an internet connection these days. You might perhaps be able to handwave something that spreads silently and effectively with a long incubation period, then suddenly activates and kills everyone in short order.

In Oryx and Crake

a bioweapon is hidden inside a wildly popular pharmaceutical product, allowing its dissemination across most of the planet before it was activated and spread "naturally".

In The Stand,

once the superflu (also a deliberately engineered bioweapon) outbreak becomes apparent it is deliberately spread by military agents already sited in foreign countries to ensure that everyone suffers from its creator's carelessness.

There are many other fictional examples you could take; this is a very, very common trope. In The Day of the Triffids, for example, the titular hazards (which may or may not be bioweapons) spread far and wide long before a separate catastrophe prevents humankind's ability to keep society together, at which point the triffids become a massive and dangerous threat overnight. And so on.

It could be waterborne but then I wouldn't know what to do with the need to drink liquid.

Modern water treatment is extremely effective at killing and filtering things down to the size of viruses, so this mechanism of spread seems likely to be a poor choice of infecting a modern society in a reasonably developed country.

Stick with the traditional means of spread, they work well enough. Measles is perhaps a good model, as it is extremely contagious and is spread in droplets that can survive on exposed surfaces outside of a host for several hours. The Stand uses a souped-up version of influenza, another favourite that can spread quickly and has been known to cause deadly epidemics.

Answer 2

Earth is huge. It is really HUGE! No realistic pandemic illness (virus, parasite (malaria), fungi) can spread all over the globe in days or even in months. Even if it is spread intentionally. Even the worsts (deadly!) pandemics in human history never hit even a percent of all living humans on Earth at that time (okey-okey, Spanish Flu - never hit even a third of population! But still less then percent of Earth's population of die off - it was not as deadly for infected as plague in medieval Europe)

So, you will need a very long incubating period, low virulence - danger by itself (if people die too fast, virus would die off with them, leaving great number of quarantined survivors), inability of modern medical institutions to find any cure for decades.

My preposition: make HIV to be transported by skin contact (or/and by air - like flu). It will infect all the population rather quickly (in a decade or so), and silently (no visible symptoms for years - a lot of people will be infected without knowing it). Humans will start to massively die off in about 2-3 decades from start of mutation. Even those who are not infected - due to pandemic of other opportunistic infections, like tuberculosis or superflues, or many many other. Little can be done in this scenario, even if HIV mutation is detected immediately - you can't guarantee that you have all infected in you quarantine, due to lack of symptoms.

To defeat it humans need to mutate by themselves and find a way to spread this mutation among survivors.

All this process of extinction would last for about century or so, with pike of die off at 40-50 years from year zero.

Answer 3

Space germ

Good old Andromeda Strain! Supergerms from space.

The Wildfire team, led by Dr. Jeremy Stone, believes the satellite - intentionally designed to capture upper-atmosphere microorganisms for bio-weapon exploitation - returned with a deadly microorganism that kills through nearly instantaneous blood clotting. Upon investigating Piedmont, the team discovers that the townspeople either died in mid-stride or went "quietly nuts" and committed bizarre suicides.

The good thing about space source is you can have the germs trickle down uniformly thru the atmosphere. Also space germs can violate terrestrial biology. If you need to get into the weeds about how exactly the space germs work, you can invoke alien biology, human engineered bioweapons (with work being done in space to prevent contamination) or even alien engineered bioweapons with the aim to clear off earth life and allow colonization.

Crichton even presents the possibility of fluky chance immunity as you want for your scenario; see link. For example, your protagonist is growing Chinese herbs in a greenhouse in Wisconsin and often sleeps in the greenhouse. High blood levels of two of these herbs are needed to block infection. Because she is in the business, she already knows the other survivor: her eccentric customer in NY.

Answer 4

This is similar to something that I have thought about a few times. As Ksbes has mentioned, the Earth is a really big place, and most natural viruses that could fit your scenario either spread to slowly, and are discovered before it has a massive impact, or are so fatal that it cant spread fast enough. So we have to look at a bio-engineered death bringer. It is made by a well funded group of people, as bio-engineering is extremely complex, and out of the scope of a one man operation. This group wishes to bring destruction to the west, and decides to release their virus. They are not stupid, and so have a bit of strategic planning for this release. They target several of the world busiest airports for the initial infection. (The worlds current busiest airfield is Hartsfield-Jackson Atlanta International Airport (Georgia, US) -- 107.4 million passengers traveled through in 2018, a daily average of 294 246 thousand passengers). The combined top 5 airports have almost 1.3 mil daily passengers. The virus is an airborne pathogen released into the air vents from a powdered source like anthrax. After initial infection the virus has an incubation period of 7-10 days, after which the first symptoms appear. These are very minor, and only intended to spread the virus further, and include coughing and sneezing and a runny nose. During this stage it is extremely infectious and spreads rapidly to everyone in close proximity to the initial infected. After about 5-9 days, the symptoms clear up, and the virus begins to progress to its final stage. This stage has rashes, boils filled with virus pus, open blisters and respiratory problems similar to TB. The victim will finally die from multiple organ failure/ total system shutdown. The last stage last for about a week, giving a total time from first infection to death of 20-30 days.

Take away points: Bio-engineered, so will be believable with small amount of hand waving. Large scale initial infection. +1 for carrying out during a peak travel time, such as before Christmas/New Years. +1 If you release virus over a 2-3 day period, increasing the inital infected population. Incubation period allows for infected to spread out relatively far before symptoms first occur. Minor symptoms, no one goes to the doctor or hospital for the common cold, which this mimics. Highly contagious, think about the common cold, when one person in a house gets it, within a few days, everyone in the household has it. Hard to prevent death, organ failure is one of the hardest medical complications to stop. +1 that by the time the final stage starts for the first infection group, a majority of medical professionals are also getting sick. And a final +5 if you have the dead bodies, with all their open blisters and leaking boils, highly contagious like Ebola. Should also fly under the radar for long enough, as no news channel is going to report on the unusually high number of cases of the cold this season. Once it is seen that its extremely serious, well, to bad and to late.

Answer 5

To produce large numbers of deaths there are certain things a disease has to do.

It has to be easily transmitted. Airborne is probably ideal, especially in this age of international travel. But transmission through sweat is pretty nasty. So you want something that can be transmitted through brief non-direct contact. Somebody sneezes and it infects a room full of people. Somebody touches a door knob and it infects the next thirty people who also touch the knob. Somebody uses a cash machine in an airport and it forms the nexus of a new source of infection. Somebody pumps their own gas and the next 50 people who use that pump get infected. And so on.

Next, it has to have a long period where it shows no symptoms but is still infectious. If everybody who gets it starts feeling sick within minutes they won't have time to infect anybody. And the authorities will know something is up very quickly. If nothing else, the elites will hide in their basements and avoid getting infected themselves. So if nobody has symptoms for, say, three weeks, it gives the disease time to spread around. You can even have some good chance at getting to lots of those semi-nomadic tribes who have their once-per-week visit from the tourist-locusts. Snap-snap, grin-grin, tip-tip, infect-infect, say no more. It will even have a good chance at catching some of the people who work in various military bunkers but get every other weekend home with the family.

As to a "herbal remedy" that's kind of tough. Maybe a herbal control. I'm thinking of tonic water and malaria.

So what about: air borne malaria with a three week latent period?

Answer 6

You could have it spread on purpose by some shadow organization. They might even have "good" intentions, reducing fertility with the virus to reduce human population as a smooth way to safe the planet or something like that. But something went wrong and the virus that was intended to sterilize half of the infected now kills 99% of them.

There is another problem though that pretty much always gets ignored when a scenario like that is invented. You want the planet to stay inhabitable and therefore you don't want a nuclear disaster. But by killing most of the population you will get a nuclear disaster anyways.

There are about 450 nuclear reactors worldwide, with about 60 more being built at the moment. And thats only the civilian ones. Without technicians to keep them in order and a supplying industry that delivers spare parts, they will all melt down. And not only the active reactors, also the stored nuclear waste from reactors, when not actively kept cooled will eventually melt and polute the environment.

Same is true for chemical waste dumps and alike.

So removing humans in short time will always result in a massive environmental disaster. Also removing them slowly through distress will very likely have the same result, as a dying human race would probably not care enough to make sure the leftovers don't poison the planet and instead focus their efforts on avoiding their own extinction.

Answer 7

A pandemic is caused by the spread of an extremely contagious virus, likely either airborne or droplet-borne. On top of that, you need a lot of international travel and either ignorance, apathy, incompetence, or malice from governments and other organizations for the virus to travel across borders.

The problem here is this requirement:

Should kill most of the worlds population leaving a few people to restart life.

If this were true for a virus, it will set off alarm bells, triggering swift response of targeted quarantines that contain the virus and keep it from becoming a pandemic. Pulling from recent history, part of the reason that governments did not act early enough to contain COVID-19 was because the virus is less deadly than its cousin, SARS. It did not raise alarm bells in the same way that SARS did. Perhaps things may have turned out differently if it were more severe, but that's just speculation from a layman such as myself.

If the virus is deadly enough, it makes nuclear bombs a viable containment/eradication strategy (albeit overly destructive), which only costs a few million lives instead of 99% of the world's population. If the outbreak started in a highly authoritarian country with no respect for human rights, you can bet your ass their government is not going to have any qualms with dropping a nuke on the source of the outbreak.

There's also the issue of how such a virus would evolve. Natural selection tends to select viruses that are contagious but not very symptomatic because populations can and will adapt to its presence. People might start wearing masks or isolate themselves in order to reduce the spread. Viruses do not have goals and the ones that proliferate are the ones that either aren't symptomatic (and thus don't give any reason for the infected to wear a mask) or are somehow contagious/robust enough to counteract common mitigation measures. The virus isn't driven by some deranged mastermind plotting to kill humanity.

This kind of suddenly-deadly virus does not mutate overnight, nor does it mutate in lock step. One virus "cell" (or whatever a single instance of a virus is called) might have picked up a mutation and survived to infect a new host. Maybe it's a little more severe or a little more contagious. But it's astronomically unlikely that a freak mutation is going to change a virus enough for a single virus particle to conquer the world. It's going to have to be genetically engineered to get what you're looking for.

There's also the issue that a virus that almost always kills its host is going to have trouble spreading. Ebola never really made it outside Africa, for instance, and it had a death rate of 90%.

Honestly, you don't want a virus for this kind of plot point. You want divine intervention a la Noah's Ark.