When the first few cases of Ebola started appearing in Guinea in December of 2013, researchers initially thought they were dealing with malaria or Lassa fever, both endemic diseases in the area. Unsure of what they were treating, scientists sent samples to labs in France and Germany for testing. After weeks of deep sequence genetic testing, they had their answer: They were dealing with an outbreak of the Ebola virus.
The delay illustrates two major issues involved in diagnosing disease––the time lag to accurately diagnose certain diseases and the lack of on-site diagnostic tools. By the time the researchers knew they were dealing with Ebola, many of the patients whose samples they were testing likely had already died.
Ebola is especially dangerous because it can spread quickly through population centers and, if not treated quickly, lead to death. In order to slow this spread, doctors needed to rapidly diagnose and start isolating and treating patients. However, doctors in resource limited-areas like western Africa lack access to rapid diagnostic tests. Instead they need to send samples to larger cities with more resources that can use more complex tests like the polymerase chain reaction (PCR) test.
While this test is highly accurate, getting results takes time––something patients don’t always have.
“There was really not a diagnostic that was ready that met the needs of the outbreak, which were to be portable, to be easy to use and to be very sensitive,” says John Connor, an Ebola researcher at the National Institute of Emerging Infectious Diseases Laboratory in Boston. “The PCR assays were very sensitive, but it wasn’t portable and wasn’t particularly easy to use.”
Since the beginning of the outbreak in December of 2013, several new diagnostic tools have been created, aimed at being more sensitive and faster to use than those currently in the field.
One new test, developed in conjunction with Tulane University and the company Corginex, uses a drop of blood for diagnosis, often delivering results within fifteen minutes, and searches for Ebola proteins rather than nucleic acid. Researchers at the Chinese Academy of Sciences also recently developed a test using magnetic nanoparticles that can latch onto viral antigens––substances from a virus that trigger an immune response. This test is said to be cheaper and 100 times more sensitive than the current ELISA test in the field in Western Africa. Since the start of the epidemic, other companies like Luminex and OraSure have also developed their own rapid tests that detect antigens from a small blood sample.
While Ebola was the most recent virus that required advanced diagnostics, other endemic diseases like HIV and Malaria have seen similar advancements in diagnostic tools in the last decade.
After HIV was first identified as the virus that causes AIDS, the FDA approved the use of the first commercial blood test or the disease, called the ELISA test, in 1985. This test, which is still used today to detect other viruses, including Ebola, detects antibodies to HIV in blood samples. The drawback was that the diagnosis took time, as patients had to wait for the antibody reaction to occur.
Today, researchers use rapid diagnostic tests to determine whether patients have HIV. Currently, one of the fastest and most non-invasive AIDS test allows involves taking a sample of saliva rather than blood.
“You stick the paddle under your tongue, incubate for 5-10 minutes and it’s essentially like a pregnancy test where it’s a bar or two bars that lets you know if you’ve got the antibody,” says Dr. Donald Thea, a professor of Global Health at Boston University who studies infectious diseases like AIDS. Thea says the goal is a diagnostic tool as quick and easy as a pregnancy pee-stick. “That’s kind of the goal. That’s nirvana.”
As with AIDS, the diagnostic tools used for malaria have also gone through major advancements. But while the rapid tests for malaria make diagnosis easier, their implementation also showed the trade-offs with using more of these rapid tests, says Dr. Hamer, a professor of global health and medicine at Boston University.
These newer, faster malaria tests look for antigens to the disease, like the Ebola tests, but they don’t tell the doctor about the specific strain of malaria parasite like a blood smear does, which could affect treatment, says Dr. Hamer.
Although diagnostic tools have come a long way, researchers like Conner feel that the best option is one tool that can test for multiple viruses at once.
“When people show up sick, they can show up sick with any of a number of different diseases where they look really similar but the treatments are different,” Connor says. “One of the big problems is that the places where you have the least ability to conduct multiple tests are often the places where you need to do the most testing.”
Connor’s lab, in conjunction with other universities and research institutions, has been developing a small chip that contains antibodies for a variety of different viruses. Once a patient pricks their finger, blood flows over the pathway in the chip, which is inserted into a computer with a microscope. From there, researchers can which antibodies react with the blood.
According to Connor, the entire process should take about 15 minutes, and researchers should be able to determine all the viruses a patient has in a single sitting.
“We are trying to develop a diagnostic that is really easy to use, that is inexpensive and that is rapid, and we think that solves a lot of the problems that currently exist in diagnosis,” says Connor.