Save the Children in Solomon Islands says two more children have died from rotavirus in the past week in Western Province.
The head of logistics and emergency, Graeme Kenna, says the latest cases brings the total number of deaths from the outbreak to 18 in the past three weeks, all of whom were children.
He says the government and aid agencies are putting a lot of work in to try and stem the outbreak by distributing hygiene kits and cleaning out wells.
He says parents need to be aware that diarrhoea and dehydration caused by the illness can be treated.
"Rotavirus need not necessarily be a fatal disease but a lot of people don't have the money after the flooding, they don't have the money to take their children to a clinic, or they don't have the means to get to a clinic because of travel."
Graeme Kenna says the struggle to contain the rotavirus outbreak has been compounded by recent confirmation of 24 cases of leprosy diagnosed in people living in temporary accommodation following April's floods.