When a person is infected with HIV, the virus never truly goes away and remains in the system like a pool, which has recently been revealed to be much larger than previously estimated.

Scientists from the Howard Hughes Medical Institute (HHMI) found in a new study that the HIV reservoir in an infected person's system is up to 60 times larger than previously though. The study, published Thursday in the journal Cell, signifies a setback among several advancements in the search for a cure to HIV and AIDS.

"The findings suggest that there are a lot more of these proviruses that we have to worry about than we thought," study lead author Robert Siliciano, an HHMI investigator at Johns Hopkins University, said in a news release. "It doesn't mean that it's hopeless, but it does mean we need to focus on getting an even clearer idea of the scope of the problem."

HIV targets a patient's T-cells and breaks down the immune system. Since it does not truly go away, preventing the virus' affects depend on keeping it at bay. Scientists have yet to learn how to get rid of inactive viruses, also known as proviruses. They also did not know how big the pool, or reservoir, of proviruses is.

In the case of the three-year-old Mississippi girl who was born with HIV and who is now nearly HIV free, her doctors will not declare her cured because the virus still exists in her system.

"For people that are working on HIV, figuring out the size of the reservoir has been a really critical issue," says Siliciano. "The field has struggled with what you even measure in people who are participating in eradication studies. How do you know how much virus is left?"

Antiretroviral drugs target active HIV cells, so scientists are calling for a drug that can fight provirus cells. Siliciano and his colleagues agreed that previous tests to determine the size of the virus reservoir were inaccurate and unclear. While somewhat discouraging, the new method of testing will be more accurate, as it will also measure composition.

Ya-Chi Ho, an HHMI international student research fellow, said there is more work to be done, such as determining how a provirus can be reactivated. Ho said it currently appears to be random and not much is known about it anyway.

"In the (Mississippi child's) case, there are no memory T cells at the time of birth, and that's why the infection is curable if you treat on the first day of life," Siliciano told Fox News. "So for the vast majority of patients to cure them, we'll have to deal with this reservoir. These cases of cures are exciting and have given people the feeling that 'Yes, maybe this is something we can do.' But it's going to be a long and difficult struggle."

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