According to the World Health Organization, malaria is responsible for approximately 445,000 deaths every year. That number may be due to drop, however, as scientists have found that a human-safe blue dye kills parasites in patients' bloodstreams within two days – that's faster than has ever been possible before.

When a person is bitten by a malaria-carrying mosquito, one-celled malaria parasites enter their red blood cells and split into male and female sex cell parasites known as gametocytes. Should another mosquito then bite that person, they suck up those gametocytes, which mate in their stomach. This results in a batch of new malaria parasites that make their way to the mosquito's salivary glands, where they can infect another person whom the mosquito bites.

Ordinarily, malaria is treated with combination therapies based on the drug artemisinin. Unfortunately, however, even after the treatment ends, the gametocytes can remain in the patient's bloodstream for up to several weeks. This means that any mosquitoes which bite them in that time can still spread the disease to another person.

That's where the methylene blue dye comes in.

In field tests conducted in Mali, it was added to artemisinin-based medication, and was found to eradicate all gametocytes in patients' bloodstreams within as little as 48 hours. The dye is typically used in laboratories to distinguish dead cells from living cells, and was reportedly well-tolerated by the test subjects. It does, however, have one interesting side effect.

"I have used it myself, and it turns your urine bright blue," says lead scientist Teun Bousema, of the Netherlands' Radboud University. "This is something that we need to solve, because it could stop people from using it."

Also taking part in the project were scientists from the University of California - San Francisco, and the Malaria Research and Training Center.