"The day before his 10th birthday, our son Jonny was run over and killed before our very eyes while we were on a family bike ride with him and our other two children."

This tragedy turned Susan Hillis' family upside down. The following day, she says, was the "valley of the shadow of death". 

But Susan's grief inspired a passion to care for children who had lost their parents. A few months later, she adopted a brother and sister – Alex and Anya – from an orphanage in Russia. Anya soon began to pray for her best friend Katya from the orphanage to find a family like they had, and it became clear to Susan that they were the answer to that prayer, too. When they went to the orphanage to begin the adoption process, it turned out that Katya had two brothers. So Susan adopted them all.

"With these seven children, we were barely surviving between work and homework and extra-curricular activities. In the midst of all this, Alex marches in and says, 'Mommy, today I began to pray God will let me go back to Russia and find my other three sisters and adopt them!' One week after this prayer I am on the phone with a friend from Russia, who says, 'Susan, I have some interesting news for you.' I thought he was going to tell me his one-year-old had just started walking, but instead, he says, 'Today I got a call from the Department of Education. They told me that Alex and Anya's other three sisters have suddenly become orphans, as their daddy burned to death in a house fire and their mother disappeared.'"

Susan was due to travel to Russia the following week, so she met the three little girls to tell them they had a brother who loved them and prayed for them. And eventually, she adopted them too, "in answer to Alex's faith-filled prayer of shameless audacity".

Fifteen years, 11 children and five grandchildren later, Susan thanks God for the way her children have blessed her.

"The path had its glories and its trials... jail sentences, addictions, teen pregnancy, and valedictorian, missionary, sculptor, state wrestling champion. And 'through it all, my eyes are on Him... and it is well, it is well, with my soul.' And we have all learned about unfailing love. It always multiplies."

Susan is an active duty officer, carrying the rank of Captain in the US Centre for Disease Control. She provided leadership in the US' response to the Ebola outbreak in West Africa, she holds a PhD in Epidemiology and speaks fluent Spanish, Russian, and some German.

And now she faces the greatest challenge in her life. She is on a mission to change the lives of the billion children who have experienced violence and sexual abuse, a figure she and her colleagues uncovered while researching this report. The focus was on objective measures of children experiencing violent behaviours, including being kicked, choked, beaten, hit repeatedly with a weapon or object; being subjected to pressured/forced/unwanted sex; hearing a parent or caregiver say they wish they had never been born or threatening to throw them out of the house; being bullied or involved in a fight; or being a victim of dating violence.

Once children have experienced sexual abuse and physical violence it increases their risk of injury, HIV, sexually transmitted infections, teen pregnancy, mental health problems, suicide and involvement in sex trafficking, as well as increased risk of cardiovascular disease, cancer, chronic lung disease and diabetes. According to this report, in the USA alone the total lifetime economic burden associated with child mistreatment was $124 billion in 2008.

These consequences are not theoretical to Susan – most of her adopted children have had to face these types of knock-on effects of their earlier abuse. 

Because of her research into the long term-impact of violence against children, Susan has been able to help lead a team of senior scientists from the CDC, who together developed seven key factors that she believes will help fight for the protection of children:

Training in parenting

Household economic strengthening

Reduced violence throughlegal protection

Improved services

Values and norms that protect children

Education and life skills

Surveillance and evaluation

Susan's work in the areas of violence against children has led to consultations with key leaders from the DAVOS World Economic Forum, the World Bank, and the United Nations. It has also led to special invitations to share this news with leaders of the global church.

When asked what matters most to her and why, she says: "replacing violence with love for a billion children, because the Lord desires that every child thrives".

"This, just this, is my passion. It is my passion for me. It is my passion for you. It is my passion for every child. So where can you begin? By this, simply this. Loving one. Yes, that's all. Love and help one. All of us, doing just this, will care for the billion. Because all a billion is, is this. One times a billion. There are enough of us to love every one of them."

Susan is a rare and unusual combination of scientific acumen, unstoppable passion and down-to-earth approachability. As a deep and sincere Christian, a world class scientist, and a champion for adoption there is something incredibly infectious about her. There are a billion reasons why I pray that God would continue to use Susan's many gifts as she serves Him at the cutting edge between science and the church.

Krish Kandiah is a contributing editor for Christian Today, and the founder of Home for Good.