Help me design a future supervirus plague / pandemic

Question

In my story, a Big Bad engineers a virus which is given to a certain segment of the population (between 10 and 20 million people) under the guise of a universal flu vaccine. Instead of preventing the flu, it infects everyone who receives the vaccine and kills them. But I want the virus to mutate (unintentional side effect) and become contagious, spreading rapidly across the country and killing 80-90% of the population of the U.S. within a short period of time.

1) The story is set 20-30 years in the future, so future tech can be included

2) It can be engineered from more than current virus

3) Early symptoms should imitate common cold/flu symptoms, cough, sneezing, headache, so people continue to go out and spread the disease

4) fast acting and extremely high death rate

5) Mutates and becomes highly contagious

6) Because there are millions of "patient zeroes", I'm hoping that the virus could not be quarantined effectively and will quickly (within a few weeks, preferably) wipe out 80-90% of the U.S. population.

7) It does not need to wipe out the whole world, though I imagine millions would still be infected and die in other countries. The primary target is the U.S.

Any ideas to help me design my supervirus? Thank you!

Answer 1

In general terms, you have something that's based on the influenza virus and still enough like that to be considered a strain of flu. So, in general you made at least two important edits: one that makes it kill the host, and one which disables the ability to spread through the air.

How to make it kill

In simple terms, it carries instructions not just for replicating itself, but for producing a toxin. Consider in particular how Tylenol can kill from taking too much, by poisoning the liver. This is a delayed death, three days after the overdose and initial recovery of the immediate symptoms.

Furthermore, this is used as a medication when sick, to help feel better! So, how’s this for evil: The virus causes the infected cells to produce acetaminophen, as well as parts to make more virons and the escape mechanism. This will mask the initial flu symptoms, and they won’t realize they are sick! But, a normal course of infection will result in a cumulative overdose over a period of a few days.

How to inhibit contagiousness

The virus still needs to spread within the body, to infect more cells. What we disable is robust airborne transmission. If the infection, caused by injection, affects tissues other than the lungs, that might not cause the runny nose loaded with virons to spread. But, that's the tissue it’s meant to infect, so it would seem difficult to change.

The virus has a way to survive in mucous or water for days, and this is in contrast to many germs which don’t. So, the specific way it’s wrapped up and packaged can be modified. Make it not survive in mucous at all. Make the contents go stale after a few minutes, or break open when taken out of water. This is basically removing or messing up its carfully honed ability, so it’s easy to mess it up.

How the plans go wrong

In the wild, flues from people, ducks, and pigs living close together will undergo reassortment when two different virus strains are present in the same individual.

The new reassortant strain will share properties of both of its parental lineages.
Reassortment is responsible for some of the major genetic shifts in the history of the influenza virus. The 1957 and 1968 pandemic flu strains were caused by reassortment between an avian virus and a human virus, whereas the H1N1 virus responsible for the 2009 swine flu outbreak has an unusual mix of swine, avian and human influenza genetic sequences.

The engineered strain has the toxicity added and the ability to spread outside the ody removed.

This is given to a person who already has (normal) flu virus in his blood! When reproducing, the self-assembly of virons will naturally mix and match parts from both strains. You get the code for contagiousness restored, or the special engineered killing code added to the wild strain, or both.

Answer 2

Well to be contagious you want to spread as many bodily fluids as possible. Sweat, snot, coughing, diarrea, perhaps bleeding. Get it everywhere. Preferably with a long incubation period characterized by lots of sneezing and coughing.

As for how it became deadly. let it mutate with an existing flu strain. Perhaps a farmer got a strain of bird flu and it interacts with your supervirus. He could even transmit it back to his chickens. Who then pass it on to local birds. Maybe birds are carriers and not themselves affected by it. Thus the birds spread it everywhere as they migrate.

With the long incubation period things have time to spiral out of control.