A certain part of the continent is currently dealing with a plague of undeath. It takes many forms, with corpses rising from their graves, strange creatures roaming in the night, seemingly driven by some unknown malicious presence. To the humans who have the bad luck of calling these lands their home, the most dangerous strain is possibly vampirism, which some would call a curse and others a disease - both correct in essence - and which differs by the manner that this infection affects the living rather the dead.
Of course it would be easiest if the cities could just shut their gates and its people cower behind their walls (the village folk not having such an opportunity), but alas that is not possible. People must eat,and for that they need farmlands and other resources that cannot be found or produced inside the walls. Trade must happen and travellers must take the dangerous journeys between cities and villages. And as the undeath looms for years in the lands, so do the cities and people survive it.
That however brings forth the question: How do cities protect themselves from vampirism?
And to clarify, how to protect from vampirism - the curse/disease getting into the city, threatening to infect the people (and cause deaths through vampires that it will inevitably create). The question is NOT about how to protect the city from vampires - individuals who have contracted vampirism, have already turned and may or may not intend to get into the city.
- Tech level would be comparable to late medieval ages, no gunpowder
- Medicine slightly more advanced than late medieval, there are actually some plants and materials with magical properties, which can be used in medicine to some extent
- Magic does exist but is generally rare and has limited capabilities (in human hands). One can assume each of the cities in question will have one mage, possibly with an apprentice
- The cities will have city walls, but not the entirety of buildings can be encompassed by them.
- The cities may have sewers
- Scholars and mages are well aware of vampirism and its characteristics, the common folk are less educated and can have some misconceptions, but are aware of vampirism.
So a few more words about vampirism and vampires, so everyone know what we're dealing with.
How can one be infected?
The infection can be contracted in two ways. One is to be bitten, but not killed, by a vampire (typically that only happens if a vampire is forcefully removed from the victim, as a feeding vampire will have the instinct/compulsion to suck the victim dry. A person who dies during the feeding will be, well, dead and not turn into a vampire.
Second way of becoming infected is to be bitten by an animal that carries vampirism. While animals themselves do not become vampires, all mammals can act as hosts for vampirism and infect through bite. Being the carrier of vampirism also makes them more aggressive and more likely to bite, a bit like rabies.
Once a person is bitten there is one last resort to attempt to avoid infection - if the bite is on a limb, removing the limb might save the person if done quickly enough. And since we're dealing with slightly better than medieval-ish levels of medicine, well...
What happens after infection takes toll?
An infected individual enters a period which we can call incubation or which the scholars would call penumbra. At this stage they're still human and alive. Penumbra may last from a couple days to a few weeks, depending on the individual, with factors impacting that time not being fully known. During that time the person may experience brief episodes of photophobia, or sensory overload from their senses becoming enhanced for short while. At the same time they will gain immunity to other diseases and will gradually become less and less sensitive to pain. There is no cure, but the infection can be "stopped" - if the person in penumbra is killed, they will NOT turn into a vampire.
Penumbra ends with the process called umbra, which is a fancy way of saying "vampirism-induced agony". And that's exactly what it is - the person will feel a lot of pain and eventually die as their heart stops and a few minutes later they will reawaken as a vampire. It is important to note that once a person enters umbra, there is no way to stop the turning, even if they are killed by some other measures, they will still rise as a vampire.
Vampirism Stage I
And so we have our vampire. For the purposes of this question all I consider important is the following (ask in comments if something is important that I didnt think to list):
The vampire retains their memories, intelligence and personality they had in life.
The vampire must feed on human blood. It is necessary for surival, but is also an addiction. As the vampire drinks when not thirsty, the vampirism will progress, further twisting their mind and body.
The vampire in the first stage exhibits following external traits: pale skin, red eyes, fangs. They also do not have a heartbeat and they only need to breathe in order to speak. As it progresses they will become increasingly deformed and inhuman (with final stages of vampirism leading to becoming a feral beast of the night)
The vampire has improved senses, strength and endurance. Later on, they can also gain limited magical capabilities - these typically only work at night and are mostly magic that is useful in combat. Some other examples include creating illusions or control over undead.In any case, these abilities will not be present in newly turned vampire so are less of a concern when it comes to that.
The vampire is immortal and their wounds will regenerate. It is only vulnerable to magic, certain enchanted items and wraithwood (understandably valuable material in these parts). They are also somewhat vulnerable to silver, as it will cause pain and wounds that are hard or impossible to regenerate, but will not kill them outright. While suffering from photophobia, vampires can still walk in daylight during the early stages of vampirism, it is only as it progresses that sunlight becomes deadly to them.
There are a couple things to consider when coming up with answer to this question. In my mind the most likely ways of infection getting into the city is either by an infected traveler - be it a member of trading caravan or a villager looking to sell their products - or animals which carry the disease, such as rats or bats. While thinking of using cats to get rid of rats I realized that cats themselves are vulnerable to being bit and spreading infection, so I thought that perhaps snakes can be kept as pets instead for pest control (being reptiles and not mammals, they cannot be hosts to vampirism).
Anyway, with all that, let me reiterate the question: What measures can be taken by the cities to prevent or at least significantly reduce the risk of vampirism getting into the city and protect the population?
In response to comments:
How long can a vampire feed before starving?
Well strictly the answer to that would be about 2-3 weeks when talking strictly about starvation. The thirst, however, will become very hard to ignore as soon as one week has passed, driving the vampire to feed. And of course the temptation of drinking blood, that never really goes away, even if the vampire isnt thirsty in the moment.