The unprecedented social and economic crisis caused by the coronavirus pandemic will see nearly seven million more children experience stunting as a result of malnutrition, the United Nations said Tuesday.

Even before COVID-19 there were an estimated 47 million children under five who were moderately or severely wasted, most living in sub-Saharan Africa and southeast Asia. 

Now as lockdowns and international trade routes disrupt vital aid supplies, the UN warned that the coronavirus pandemic could have an "intergenerational effect" on the health of millions. 

Writing in The Lancet medical journal, a team of experts showed the results of computer modelling estimates on food supply in 118 poor and middle-income nations.

They found that the prevalence of moderate or severe wasting among under-fives would increase 14.3 percent -- equating to an additional 6.7 million cases. 

Wasting occurs when the body is so acutely malnourished that its muscles and fat begin to diminish. 

A host of research initiatives have shown clear links between wasting and chronic and severe health conditions later in life.

"The profound impact of the COVID-19 pandemic on early life nutrition could have intergenerational consequences for child growth and development and life-long impacts on education, chronic disease risks and overall human capital formation," wrote the researchers.

The models showed that in the worst case scenario where the pandemic could cause young children to miss 50 percent of their nutritional care and treatment services, nearly 180,000 could die this year alone.

Wasting is responsible for one in 10 infant deaths in low- and middle-income countries and recent research suggested the pandemic will throw an additional 140 million people into extreme poverty -- that is, living off less than $1.90 a day.

In countries already experiencing a humanitarian crisis, the United Nations' children's fund has warned that up to 100 percent essential nutrition services could be disrupted. 

An accompanying open letter signed by the World Health Organization's chief Tedros Adhanom Ghebreyesus said that this could be alleviated somewhat, but that aid agencies need a minimum additional $2.4 billion to protect at-risk children. 

"We must step forward together with sustained action and investments on nutrition today and deny the COVID-19 crisis and intergenerational legacy of hunger and malnutrition in children," it said.