Most stings occur during the summer wet season in October–May in North Queensland, with different seasonal patterns elsewhere. Because the jellyfish is very small, and the venom is only injected through the tips of the nematocysts (the cnidocysts) rather than the entire lengths, the sting may barely be noticed at first. It has been described as feeling like little more than a mosquito bite. The symptoms, however, gradually become apparent and then more and more intense in the subsequent five to 120 minutes (30 minutes on average). Irukandji syndrome includes an array of systemic symptoms, including severe headache, backache, muscle pains, chest and abdominal pain, nausea and vomiting, sweating, anxiety, hypertension, tachycardia and pulmonary edema. One unusual symptom associated with the syndrome is a feeling of "impending doom". Patients have been reported as being so certain they are going to die, they beg their doctors to kill them to get it over with. Symptoms generally abate in four to 30 hours, but may take up to two weeks to resolve completely.