It exists mostly among children from poor families.

它主要存在于贫困家庭的孩子中。

youdao

In 2008, there were 247 million cases of malaria and nearly one million deaths - mostly among children living in Africa.

2008年有2.47亿疟疾病例，近百万人死亡，其中大多数是非洲儿童。

youdao

Malaria caused almost one million deaths, mostly among children in Africa.

VOA: special.2009.05.26

The Joint Committe on Vaccination and Immunisation (JCVI) said the new strategy would avert a large number of flu cases among children as well as many severe cases and deaths, mostly among the elderly and others vulnerable to the infection.

BBC: Flu vaccines for all children