"Bungarus" contains some species which are among the most venomous land snakes in the world to mice based on their . They have highly potent neurotoxic venom which can induce muscle paralysis. Clinically, their venom contains mostly presynaptic neurotoxins. These affect the ability of neuron endings to properly release the chemical that sends the message to the next neuron. Following envenomation with bungarotoxins, transmitter release is initially blocked (leading to a brief paralysis), followed by a period of massive overexcitation (cramps, tremors, spasms), which finally tails off to paralysis. These phases may not be seen in all parts of the body at the same time. Since kraits are nocturnal, they seldom encounter humans during daylight, so bites are rare, but a bite from a krait is potentially life-threatening, and should be regarded as a medical emergency.