The clip shows the youngster crying: “Mum, that’s our stop, that’s our stop.”
She appears unable to stay awake and regularly scratches her scalp.
At one point, her head lolls forward and she leans on the youngster.
Another man in front of the pair also appears to not be fully aware of his surroundings.
He struggles to stand up and another bus passenger can be heard saying: “Damn bro, you need to sit down man.”
The video is believed to have taken place somewhere in the US, with social media users suggesting it happened in New Jersey.
While there it is not clear exactly why the woman and man appear in a semi-conscious state, the woman repeatedly scratches her face.
Intense itching is a side effect of opioids, including heroin.
The US has been gripped by an opioid epidemic in recent years, with 399,230 dying form opioid-related causes from 1999-2017.
That horrifying figure is equivalent to the entire cities of New Orleans or Cleveland being completely destroyed.
In 2017 alone, more than 72,000 people died from a drug overdose in the US and experts say that addiction is the most deadly issue the country has faced in the past 50 years.
It comes after a Brit woman died after being “eaten alive” by deadly drug krokodil.