More than 1,000 Iranian schoolchildren, most of them girls, have developed symptoms over the past three months. It is believed that the female students were poisoned, possibly with poison gas.

But what is the reality of the situation, and why do female students develop symptoms?

Dozens of girls in at least 26 schools across the country were reported to have developed symptoms on Wednesday, marking a clear escalation in the number of cases.

Many people have also reported similar symptoms, including respiratory problems, nausea, dizziness, and fatigue.

So what is behind all these reports, and how have cases spread across the country?