ABILENE, Texas -

An experimental serum for Ebola recently given to Nancy Writebol and Dr. Kent Brantley is raising some questions. The drug hasn’t been tested on humans yet.

The drug called Z-Mapp is created by a firm called MAPP Biopharmaceutical, located in San Diego.

Dr. Chris Tawwater, a pharmacology professor at the Texas Tech Health Sciences Center in Abilene, explained how the drug is created.

"They're taking antibodies that animals have developed,” said Tawwater. They're humanizing them, producing them in nicotine plants. After getting just the antibodies and nothing else, they inject them into humans and it's a temporary protective immunity."

Tawwater said the drug gives a temporary boost to the patient’s immune system, allowing them to fight off the infection on their own.

According to experts, although the drug has been used twice now, and both patients appear to be improving, that does not mean the drug is working. It also doesn’t necessarily mean that the drug would work on others.

Some patients might be concerned about the risks with taking an experimental drug. Tawwater said that with today’s technologies, the risks aren’t as great.

“This [serum] is a whole lot more straight forward,” said Tawwater. “Safer from an infection standpoint and also from the side effect standpoint.”

But, Tawwater said that the chances for the drug being sent to West Africa is less than likely because of the way it is produced -- making it difficult to manufacture in large amounts.

In addition to the two Americans who were infected, the numbers for the Ebola outbreak are higher in Africa, where the disease originated. The World Health Organization has reported cases in Guinea, Sierra Leone, Liberia and Nigeria.

There have been 1,603 reported cases with 887 deaths. Guinea has the highest death toll at 358, then Sierra Leone with 273 deaths and Liberia with 255 deaths. Nigeria has only had one recent death due to the outbreak.