Strains of malaria resistant to the most common drug used to treat the disease are spreading quickly along the Thai-Myanmar border, a new study has found.

The 10-year study published Thursday in the U.K. medical journal The Lancet found that unless scientists find a way to control the strains, they could spread to India and Africa.

Malaria is caused by the parasite Plasmodium transmitted through the bites of infected mosquitoes. Symptoms include fever, headache and vomiting. If left untreated, it can cause death by disrupting blood flow to vital organs.

In 2010, the disease killed an estimated 655,000 people, mostly African children.

The study looked at 3,202 patients between 2001 and 2010 who were infected by Plasmodium falciparum, a type of malaria that causes severe illness.

It found the standard treatment - combination therapies containing the drug artemisinim - took much longer to rid patients of the malaria parasites.

Part of the problem, experts said, is the drug-resistant strains are being fueled by the incorrect use of artemisinim and fake or substandard versions, something government and health agencies are being urged to stop.

Scientists don't know if the drug-resistant strains now spreading in Myanmar are the same ones that showed up in Cambodia eight years ago. They are analyzing their genes to determine if they're related.

They expect to have an answer later this year as they study the complete genome.