Health Status

Unless you really know your way into the game, a player will take damage of some sort. Depending on your luck, you may or may not suffer a condition (for example, getting infected)

Infection
If you get bitten, there is a chance the player will get infected by the virus 732-ZH. If not treated, the player will die and turn into a Runner.

A way to identify an infection, is to pay attention to the screen. If veins-like lines star growing in the edges of the screen and moves towards the center, it means you got infected. You can either use Phalanx pills to stop the infection momentarily or use a Gene therapy to treat it and become inmune (doesn't have to be infected to use it)

Bleeding
Getting attacked by a zombie or a player, might trigger the Bleeding condition. During this time, the player will bleed until it dies, and won't be able to sprint. The player will lose 1 HP per five seconds (happens every time the blood splatters to the screen or the player groans in pain)

Again, pay attention to the screen. If blood shows up in the borders of the screen, or someone else sees the blood dropping from you, it means you are bleeding. Bandages are what stops bleedings faster and regain some lost health, but First Aid Kits can also be used to regain a lot more HP but it takes longer.

Black-n-white Screen
It is a sign that the player has low HP, and may die the next time an enemy hits you. In this state, the player's screen will go black and white, unable to see properly.

It can be fixed with a First Aid Kit, to recover a good portion of HP.

Keep in mind that, due to a slight issue with damage income, a zombie of any kind can kill a Survivor in one or two hits, not even giving you a chance to heal.