The council’s public health director Andy Kingdom said the UK Health Security Agency (UKHSA) was currently investigating the cause of the spike which is yet to be confirmed.
But he added children not mixing as much during coronavirus lockdowns could be a possible cause as they were unable to pick up infections they normally would younger.
It comes as the World Health Organisation (WHO) stated an acute, severe strain of hepatitis had been detected in children from under one to 16 years old in 12 countries.
The UN body added those countries included the UK, Spain, the US, France, the Netherlands and Israel and that the strain has claimed at least one child’s life.
He added it could be staved off by regular hand washing, avoiding contaminated water and other good hygiene practices but said doctors should be contacted if a child’s skin turns yellow.
The director said: “To be completely honest we don’t know for certain what’s causing this but we’re investigating it.
“There’s a range of strains of hepatitis, A, B, C and E, and some strains affect children more like A and we’re looking at why.
“We’ve found more cases of it in London and the South than we have here so far.
“The question is why the spike is happening now.
“We’re looking at adenovirus, which normally causes colds, flu-like symptoms and vomiting in kids, and whether its genetic structure has changed.
“But another factor is that the coronavirus pandemic has likely messed up the usual, seasonal pattern of infections we’re used to, has that pattern changed in such a way that it’s brought these spikes on?
“It could also be connected with water or food contamination.
“Children normally pick up infections at a younger age, something like hepatitis tends to be more serious if you get it older, chicken pox is similar.
“Some of the symptoms of hepatitis include muscle pain, sickness and a loss of appetite, but the issue is those are common symptoms of several different conditions.
“The main and more serious one for hepatitis is if the skin turns yellow like jaundice. The way to stop it with good hygiene practices, and also as we saw with coronavirus by keeping your distance and avoiding crowded spaces.
“But such infections and the way we deal with them are part of living in a world where we’re exposed to bacteria and viruses.”