Danger of infectious vectors

Overview:

• Abstract
• Simplified analogy
• What is a vector and a prion?
• Biological weapon for mass destruction
• Utilizing an infection as a vector
• Critical importance of stealth
• Impossibility of a vaccine for the vector
• Scientific feasibility and acute danger
• Up- and downsides of research in this sector
• Conclusion

Abstract

This article highlights the danger of infections that were introduced to the human body by means of infectious vectors e.g. bacteria, as well as preventive measures. It explains how this can be achieved and what the “advantages” of these vectors are.

Simplified analogy

In order to explain the abstract in another way, let’s imagine a person got an untreatable form of cancer. There is no way the person will survive and this happened because the person had a common cold four years ago.

In this scenario the cold is the vector and the cancer is the payload of the vector aka the the dangerous infection.

What is a vector and a prion?

While vectors generally describe how to move from one spot to another, a disease vector describes an organism that can transmit pathogenes (infections) to other individuals (World Health Organization, 2024).

This article expands the definition of a disease vector (only called vector from now on) by including viruses that can transmit pathogenes to other individuals as well¹.

A prion is a protein normally found in the human body, but in a misfolded form. First sympoms can take years to develop, but from then on becomes quickly fatal. Currently, there’s no cure or vaccine for these prions and they usually if not always lead to death due to damage to the brain (Centers for Disease Control and Prevention, 2024).

They propagate by turning properly formed proteins into the misfolded ones and don’t require DNA for replication (Biology LibreTexts, 2024).

Examples of prions are the Creutzfeldt–Jakob disease or the mad cow disease. In theory, it should be possible that prions affect proteins not in the brain while still being deadly, but in this article, I will stick to prions for the brain. Other versions would still follow the same principles discussed below.

Biological weapon for mass destruction

To know what kind of biological weapon could be the most destructive, one should look at its attributes:

• An effective weapon of mass destruction whose mission isn’t to kill a specific target but as many people as possible should be extremely deadly with a lethality (the chance of an infected organism to die from the infection) of up to 100%.
• Finding a cure or a vaccine for the corresponding biological agent should be as difficult as possible.
• In order to infect as many people as possible, the agent should spread rapidly before killing the individuals.

Utilizing an infection as a vector

In order to infect people, vectors are required and while most people will think about mosquitoes or rodents, bacteria and viruses are also valid options, when genetically engineered. Infectious bacteria could free viruses once in the host and infect the host as well. For this to happen, a bacterial cell that was infected with the virus would need to enter the human body, die and thereby release the virus. This virus should also be able to bind to human cells.

Another more dangerous variant would be the transmission of prions, instead of viruses. As discussed above, prions are always deadly and there is no cure or vaccine. Although not for every single virus, we already know how to defeat a lot of viruses and usually the lethality rate of a virus isn’t 100% as well. This means that prions are an easier template because they already fullfill two of the three criteria of an effective biological weapon, namely no cure and high lethality rate, whereas one would need to genetically engineer a virus to fullfill these criteria.

Because prions are only singular proteins and therefore very small, even smaller than viruses, they could be inside bacteria as well. But the bacteria don’t necessarily need to be infected, but they could simply produce them as part of their metabolism. We can already create proteins with bacteria, so this method is feasible (National Library of Medicine, 2024).

Infecting humans with prions that use viruses as vectors is more complicated. Just like the bacterium variant, the virus would need to infect the human, but a virus propagates by infecting a cell and injecting genetic material into the cell. Afterwards, the cell starts to create more viruses. If the virus injects genetic material that forces the cell to create more viruses and also a small amount of proteins, more specifically prions, we get prions outside of the cell. The result would be the creation of a lot of free viruses, which is what you expect from a virus, but also prions that then can find their way to the human brain and infect it. For the prion, it might be important that the vector infects specific areas to help it find the way to the brain (e.g. the intestines to utilise M cells). But this isn’t strictly required. The newly created viruses would still have the gene that creates prions as a byproduct, so the virus’ kids still work as a vector.

In other words, prions can be transmitted by bacteria and viruses in different ways and these prions — just by their nature — already fullfill two of the three criteria of an effective bioweapon, namely no known cure or vaccine and a high lethality. This means only one criterium is left.

Critical importance of stealth

In order to spread the prion, one could use bacteria or viruses as discussed above. To maximise the number of infected individuals, the targets should be oblivious to the actual payload (the infection that is actually dangerous). Because the prions can take years to develop first symptoms, the worst-case scenario would be that the targets only find out that something is wrong after multiple years. To maximise the chance that the people only find out when the prion’s symptoms start, the vector should be very easy to spread but show next to no symptoms while infecting new people. The lethality of the vector would, therefore, be extremely low. This could be realised by giving the vector the strength of a common cold. A cold spreads relatively fast, and only very few people go to a doctor with cold symptoms, and even fewer people will get their infection tested for anything big. This means the prion will be in the body, and nobody will find out at this point.

Even when the symptoms of the prion start, it is hard to make the connection between the vector and the prion as there would be years in between infection and symptoms. Health organisations would first start to look into meat people ate in the past as this is one of the main ways of transmission. This would buy the vector even more time to infect individuals before the vector itself would be investigated. Therefore, stealth and distractions are some of the most important factors in such a scenario. If we are lucky, intestinal or other similar problems might arise because the vector helps the prion to find its way to the brain as discussed above in “Utilizing an infection as a vector”. This would make early detection more likely but isn’t required as the prion might be able to find the brain on its own once in the body. To mimic this prion-stealth-tactic with a virus in a bacterial vector, the virus would need to stay dormant for some time. An example of such behaviour in a virus would be rabies, though the symptoms usually develop way faster than the ones from a prion making prions stealth kings. To make a virus in that direction more like a prion, one could use triggers that the virus stays dormant until later.

The virus could be activated from the dormant state if the person is for example exposed to or produces a certain protein that reacts with the virus.

For even more confusion, the payload virus or the prions themselves could also be infectious though one needs to figure out how to make prions virulent in the first place. Infectious prions or payload viruses could lead to doubts whether or not there is another method of infection in the first place. The lethality of the payload virus can also be ignored in this scenario as the transmitter virus/bacterium is the main way of infection.

Impossibility of a vaccine for the vector

A vaccine for the transmitter virus/bacterium is also hard if not impossible to get. Antibiotics for a transmitter bacterium are also ineffective.

The problem when fighting the transmitter is that the smallest amount in your body is enough to deliver the dangerous infection. Vaccines and antibiotics focus on making sure that the symptoms are more managable. This means that the payload is still delivered. For this reason, vaccines are more likely to be developed against the payload. For a virus where we might have research on how to fight it, it could be developed relatively fast, but because we don’t have any medication against prions, this variant is more likely and more dangerous.

Nonetheless, a vaccine against the vector should still be developed though only as the second priority after a vaccine for the payload.

The two advantages that the vector vaccine has are as follows:

1. Realistically, vaccines could make sure that symptoms from the vector don’t develop or are weaker, slowing infection of other people down as you can’t infect others as effectively when symptoms don’t start or are mild.

2. In the best case scenario, widespread vaccines could not only slow new infections down but could even make sure that the vector goes extinct. While this method is less likely than the first, humanity already achieved this with the smallpox. It also becomes the best chance to kill the payload if no cure for it can be found for some reason, as the infection could kill individuals faster than infecting new people, going extinct in this process.

Scientific feasibility and acute danger

But before the disease can go extinct, it has to be created in the first place.

A natural development towards this infection type is rather low. The “goal” of a natural infection is to spread and stay alive. Because this disease type would spread a secondary infection and can live even without this, there’s no pressure of keeping an infection like that. As natural selection has no pressure, the genes for the payload will quickly mutate and the secondary infection will lose the ability to infect the host cells. While it is possible that a parasitical relationship between the vector and the payload exist, the payload would need to infect human cells and the vector which is rather unlikely and unstable as two possible immunities can stop the spread (immunity against the vector and immunity against the payload). Unlike natural selection, humans could make sure that the genes for the payload production are less prone to mutation or make sure that the genes/proteins for payload production are important for the metabolism of the vector.

This leaves only the man-made variant. The acute danger here can be devided into two parts. On the one hand, we have the question regarding how difficult it is to create the infection on a technical level.

On the other hand, there’s the question of the motive of creating such a dangerous weapon.

One motive could be an attack against a certain group. A payload that is only dangerous towards a special group can be achieved by letting the vector roam freely but the payload itself reacts to a protein, a gene sequence or similar that is only produced by the group. This way, a payload could be inside one person but in the deactivated state while the infection in a person inside the group will activate the payload making it dangerous for this group and no one else, unless mutations start to show up, disrupting the checking system. The inverse is also possible, leaving only a group unaffected that has this special marker in them.

Using the infectious vectors without a precise target is another viable option for some people. Due to the fact that this version is devastating for all sides, it won’t be used in a strategic way. The most likely groups going with this kill all version, are terrorist groups that want to “see the world burn” or failing governments/groups.

The failing groups/governments can use the approach as a dead man’s switch. A group could threaten to release a bioweapon similar to nuclear retaliation if they’re attacked. They wouldn’t need to confirm that it is an infectious vector, just that they release a biological agent should their position be threatened. An outside observer can’t confirm whether or not the dead man’s switch was a bluff or is an actual infectious vector due to the long incubation period.

The fact that there are relatively few situations where one would create such a disease establishes the largest bottleneck in the likelyhood.

The technical problems are rather easy to surpass.

The biggest technical issue would be the creation of the virus or prion by the vector. As discussed above, the creation of prion by a bacteria is just a tweak of a bacteria that is already infectious and then make sure it produces prions or viruses as part of their metabolism. Viruses also just need to get a few new genes to tell the cells to produce prions along with new viruses. Importantly, the vector has to have a stable genome regarding the payload production. Because the production of working viruses and prions requires specific amino acid sequences, a small mutation in the vector might make the payload unusable. This can be counteracted by either making their genome have reduntant or gene-repairing genes. Another method would be to make the production of the payload part of the vector’s metabolism, so that it can’t survive without producing the payload

The next issue would be to make the prions and payload viruses infectious enough to infect humans with only one vector infection. Because a vector infection, even a weak one, would still create a large amount of payload, the chance of infection is high. Prions usually cannot be destroyed by the human immune system, so the immune system itself might spread the prion infection in the human body and increase the likelyhood of payload infection. Furthermore, the vector might guide the prion to a path which leads to the brain.

Viruses are often highly infectious themself, not only for healthy prion proteins, so a virus is more likely to cause an infection once in the human body.

Infectious vectors can also be enhanced with the same methods, a common biological agent gets enhanced with. For example, the vector could survive longer outside the human body or the payload might only get dangerous if a special gene or protein is present in the infected individual. This would make sure that only a special group is killed by the infection or vice versa, that only a special group survives and the rest of the population doesn’t.

Given all these parameters, researchers could gain valuable insight if such a disease is released.

The researchers could look for the specific traits of the infection and thereby find weak points that can be exploited to defeat the disease. Furthermore, they might figure out who released the infection in the first place and afterwards take further measures to extract more information on how to stop it from the people that released/designed it.

Up- and downsides of research in this sector

Given this risk of such a disease, research in this sector might still be a double edged sword.

On the one hand, one can argue that if we possess research in this area, we find easier paths to create such a biological weapon or ways to enhance its power. The only issue is that while this might be true, development in this sector will be made one way or another by researching other diseases or using infections to deliver cures for diseases. It can partially be compared to nuclear weapons. One can argue that the development of nuclear weapons was inevitable as nuclear power creates a lot of energy (as reactors) and the development of weapons from civilian nuclear usage isn’t too far. At the same time, the main reason for their fast development was the fear that Germany might develop nuclear weapons during World War 2 and therefore, the USA rushed to build nuclear weapons before Germany could do so. A similar dynamic exists here as well. It gets easier and easier to use gene editing technology, increasing the chances that one group actually finishes the development of an infectious vector.

At the same time, there’s a big difference between nuclear weapons and infectious vectors. While nuclear weapons can’t be stopped, making antidotes for infectious vectors or finding ways to search for antidotes faster is possible, therefore, making research in this area helpful and not purely destructive.

While research will, as described above, certainly make the development of these infections easier, one can try to make research in this area safer.

One way could be to not publish the methods of creating an infectious vector, but just publish the results for the given disease. A proof of concept should also censor the exact steps to create such an infection.

When creating the infectious vector, one should try to use vectors that can’t infect human beings and the vectors should mutate quickly. This makes sure that even if a disease should be released accidentally, the infection cannot affect many people before the payload’s genes mutate to make the payload useless. Only the genes that make sure that the mutation rate is high should be stable to increase the chance of payload failure due to damaged genes.

Furthermore, the payload should be a virus as there are harmless viruses that can be used to lower the risk for humans if a breach should occur.

Otherwise, standard procedures for containment of highly dangerous biological agents should be followed as well.

Another part of prevention will be finding cures for dangerous infections that could be used as payload. This method could reduce the lethality of an infectious vector. As described above, prions have some major advantages against viruses to cause more harm, therefore, research in prion vaccines or antidotes for prions should be one of the higher priorities as they could pose the biggest threat.

Conclusion

Infectious vectors could pose a serious threat as a biological weapon. They are deadly, highly infectious and the search for a cure could take years or decades. Preventive methods that were used for Covid can’t easily be applied here as the infection took place long before symptoms started and once preventive measures are taken, the chance of being already infected are high. A minor infection here could be enough to kill a person years later unlike most other diseases where a minor infection is usually a mere inconvinience. While mostly talking about prions as a payload every other variant with viruses could still be just as deadly. Prions are just easier to embed with modern technology and already check the boxes for deadliness and stealth with no cure.

While research in this sector is a double edged sword, it is still important to do research there to take preventive measures or to find cures more easily if it should come to a release. Developments in gene editing also increase the chance of attacks with such a biological weapon as non-state actors could create them as well which makes research even more important as more people could create and release them.

1: The infection can only be called a vector if the infection that the vector transmits isn’t itself which would be self-replication.

Author’s note: If you spot any mistakes in this or other articles of mine, please write a comment where you found the mistake and what the mistake was, so that I can correct it. This article runs under a creative commons Attribution, share alike license.