A condition that is entirely preventable called rheumatic heart disease (RHD), but which like in impoverished communities Africa, the Middle East and South East Asia, is continuing to impact the lives of Timorese people, and in particular the young. And often it has fatal consequences.

While the actual number of how many lives are lost and impacted by RHD in Timor-Leste is not known, researchers from a new joint Timor-Leste and Australia RHD health program believe there could be up to 10,000 young Timorese with the illness.

But while the numbers are concerning, the message being pushed in the health program is simple: the disease is preventable with regular penicillin injections.

"I feel like we have just reached the tip of the iceberg and there's a whole lot more rheumatic heart disease in Timor-Leste than what we've been able to detect with a moderately sized screening program," Josh Francis from the Menzies School of Health Research told the ABC.

Dr Francis said a big part of the strategy was to demystify the condition and explain the importance of the painful monthly injections, a task undertaken by local health worker Anary Dos Santos.

"[The success so far] is a real testament to Anary and the way he's communicated with these families and help them understand this is something that can make a real difference to the lives of their children," Dr Francis said.

After six months of the health program 1,500 children at schools in Dili, and Ermera have been successfully tested. About 50 were found to have undiagnosed rheumatic heart disease (RHD).

A severe case of RHD can result in heart failure and requires life-saving cardiac surgery, but only a select few Timorese patients can be flown to Australia for the operation.

"We were seeing very severe cases, very much at the pointy end, children who would come into hospital with severe heart failure from severe rheumatic heart disease, and with no real options for cardiac surgery," Dr Francis said.

"Tragically we just see many children who die."

The number of deaths from the disease in Timor-Leste is not known because the illness was undocumented until now.

RHD is caused by infection with the highly contagious group A streptococcus bacterium, which leads to a condition known commonly as “strep throat”.

Step throat can be easily treated with antibiotics.

But, in disadvantaged communities, where overcrowding and substandard housing is common, children are exposed to group A streptococcus bacterium constantly and often suffer from recurrent bouts of disease.

Treatment with antibiotics is often delayed or non-existent due to limited access to health services.

This repeated and prolonged infection and exposure to strep can lead to a condition called acute rheumatic fever, an inflammatory disease that can involve the heart.

As the immune system attempts to destroy the streptococcus bacterium, it can also destroy the heart by attacking the valves, which contains similar looking proteins to those of the strep bacterium.

Without antibiotic treatment to stop the bouts of acute rheumatic fever, the heart can be left permanently damaged and lead to RHD.

Without open-heart surgery to repair or replace the damaged heart valves, proper flow of blood through the heart is diminished, the heart becomes enlarged, clots can form and children are at risk of dropping dead from stroke at any time.

By working to identify Timorese patients with mild or moderate levels of RHD, and then ensuring they receive monthly penicillin injections to stop the progression of the disease, health workers say lives can be saved.

The new health program is supported by Menzies, Timor-Leste’s National hospital, the Bairo Pite Clinic and Timor-Leste Heart Fund.