Infection
An Infection is a status effect inflicted by certain zombie bites that are particularly deep. If untreated, the infection will eventually kill you. You can clean the wound with disinfectant, or take antibiotics if the infection progresses. Always keep at least one infection treatment when you intend to fight zombies, one bite can be fatal.
When wearing filthy clothing, every incoming attack has a (very small) chance to turn into an infected attack causing a bite wound.
Not the same as a traditional zombie movie infection. Might be related to the zombie 'virus' (not a virus, but that is a different spoiler), but probably just their, semi rotting, foul smelling, saliva. And the pieces of other humans still stuck between their teeth. The combination of bacteria from these sources causing some form of sepsis. Might still infect you with the zombie stuff. But that is not what kills you.
Bite wound
Zombie bites that hit and deal any amount of damage can leave bite wounds that feel "really deep...". Such a wound can easily become a serious threat; though you've got about 6 hours (3600 turns) after being bitten, you should pay attention and take care of the problem ASAP as it gets tougher to treat over time. An bodypart with a bite wound is blue in the interface.
For the first two hours (1200 turns) you'll occasionally be warned about it ("Your bite wound really hurts.").
After 2 hours (1200 turns) pass, the wound will cause you pain (up to 10 points), making sleeping very difficult ("Your bite wound feels swollen and painful.") and reducing your dexterity by one.
After 4 hours (2400 turns) the penalties will double - two points of dexterity and up to 20 points of pain.
After 6 hours untreated, the bite wound will become infected.
A healthy diet, along with relevant traits such as Infection Resistant, can help your system repel the infection on its own. The chance of this happening to new survivors without Infection Resistant is not too high (~30%).
You can clean a bite wound with disinfectant, or painfully cauterize it with a hotplate or soldering iron. It should be noted that it is not guaranteed that cauterization will be successful(50% chance), and may even make the wound worse(as if 43 minutes of infection has passed) if it fails. If you have disinfectant, use it. Once the infection's fully developed, cauterizing or cleaning won't help as it's already spread into your body. You can also cauterize wounds with a knife if you've got fire nearby (an adequately filled lighter will do).
Getting bitten in the infected body part makes the infection progress slightly faster (~7 minutes per bite if bite wound or ~4 minutes if infected wound).
Finding first aid kits and disassembling them is a good source of disinfectant.
Infected wound
Infections may develop when a bite wound isn't addressed within 6 hours. This disease will last for 24 hours. An infected bodypart is green in the interface, and shows up in the @ player info screen as 'Infected (body part)'.
After getting this disease (Infected wound), your strength and dexterity will be reduced by one point each and you'll start accumulating significant pain (up to 20 points). The constant pain makes sleeping nearly impossible. You'll also have a low chance (0.1% chance per turn) of vomiting. Since this stage of infection is still relatively mild, one has a better chance to try and find medication and healthy food to try and fight the infection.
After 8 hours (Badly Infected wound), your strength and dexterity will decrease by another point each. You'll also suffer from severe pain (up to 60 points). The chance of vomiting increases significantly (1 in 600 chance). This stage of infection makes it more difficult to loot any place in, but if one has certain medication to increase their stats at least temporarily, they may still have a chance to find something before they fall severely ill by stage 3 infection.
After 16 hours (Pus Filled wound), your strength and dexterity will be reduced by yet another point each. You'll also occasionally vomit and suffer from very severe pain (up to 90 points). Vomiting becomes frequent (1 in 200) and there's a 1% chance per turn of passing out for up to a minute. Due to the severity of this stage of infection, one is unlikely to be able to successfully search for medication for treatment of the infection, therefore, one can only try work with what resources they have as they hope to recover from the illness by themselves.
24 hours after the infection (30 hours including the bite wound) you will die ("You succumb to the infection.").
You can cure the infected wound by taking regular antibiotics (one dose every 12 hours), or using royal jelly. This will give you the "recovering" status ("Recovering From Infection") with duration equal to 4 times the time spent with the infected wound. Even with antibiotics, you may still fail to fight off the infection and die.
An infection can randomly heal on its own. A starting survivor has roughly a 15% chance of surviving an untreated infection. This chance is significantly higher with the Infection Resistant trait.
This disease can also be part of an NPC mission, where you'll be asked to bring antibiotics back.
Recovering from infection
After healing infection, the penalties are not removed immediately. It will take 4 times as long for the penalties to be removed as it took for them to accumulate. Penalties during recovery are the same as penalties during the infection, except they decrease with time rather than increasing.
For example, a survivor who healed a 10 hour infected wound (Badly Infected) will keep the Badly Infected penalties for 8 hours (4 * 2 hours), then they'll decrease to Infected penalties for the next 24 hours (4 * 8 hours).
Recovering from infection status significantly lowers the chance of other bite wounds and infections healing on their own.