PHOENIX — Amid escalating anxiety over the fast-spreading Zika virus, a team of scientists that includes Arizona researchers has developed an inexpensive test that can detect the disease even in regions with limited medical resources.
The test involves a series of biological reactions that take place not in cells, but on a strip of paper imprinted with yellow dots that turn purple when RNA, a complex molecule similar to DNA, is detected in a drop of Zika-infected blood.
The emerging technology, which costs $1, is being touted as highly accurate because it can distinguish between Zika and the closely related dengue virus.
“The cost is also really important because you can get it out to people who need it the most in low-resource places,” said Alexander Green of the Biodesign Institute at Arizona State University in Tempe.
The mosquito-borne Zika virus has spread to many countries and territories since an early 2015 outbreak in Brazil. Although the disease is considered mild and most infected people show no symptoms, it poses high risks to pregnant women. Mounting evidence links the virus to microcephaly, a birth defect characterized by an underdeveloped brain and small head in children. As of late April, Brazil’s Health Ministry put the number of confirmed and suspected cases of microcephaly at about 4,900.
In the continental United States, 157 women have tested positive for the virus, the latest figures from the Centers for Disease Control and Prevention show. Overall, 544 cases have been reported in the country, and most involve patients who were exposed to the virus while traveling. Florida has the highest number of cases.
In U.S. territories, primarily Puerto Rico, the virus has been diagnosed in 122 pregnant women. In all, 836 Zika cases have been reported on the island, with most infections originating locally. There is no vaccine for the disease and little is known about its long-term effects. The virus has caused global alarm, including concerns over visiting Brazil for the August Olympics in Rio de Janeiro.
In response to what the World Health Organization has declared a public health emergency, President Obama in February asked Congress for $1.9 billion to battle Zika. Earlier this month, lawmakers in the House and Senate approved measures granting a fraction of what the president requested: $622 million and $1.1 billion, respectively. The president said anything less than his request is inadequate and urged members of Congress to send him a bill before summer recess.
“This is something that is solvable,” Obama said of Zika during a press briefing in May.“This is not something we need to panic about. But this is something we have to take seriously.”
Stopping the spread of Zika
The quick spread of Zika prompted ASU’s Green and colleagues at Harvard University, MIT and other institutions in late January to focus on research that built on previous work. In early May, their findings were published in the journal Cell.
Accurate diagnosis of the virus is a critical step in preventing the advancement of Zika, Green said, so having a test that can discern between viruses with similar clinical signs as Zika is significant.
“If we know who’s infected and where that infection is and where it’s coming from, then we could tell if we’re preventing the spread and also what methods of preventing the spread are actually being successful.”
The paper device, which contains a mix of freeze-dried cellular components and biological proteins, needs no refrigeration and has a long shelf life. This makes it ideal for use in remote regions to test blood, urine and saliva samples for Zika and, eventually, other RNA viruses that cause illnesses such as influenza, measles and West Nile fever, Green said.
The live Zika virus used to validate the technology came from the University of Wisconsin-Madison, where scientists are studying Zika in monkeys. The next step is for Green and his colleagues to secure research funding and test the diagnostic tool using human samples.
“We need to get collaborators in South America who we can work with to test the devices,” he said of the paper-based technology.
Green is optimistic that the test, which can be performed in a couple of hours using basic lab equipment, such as pipettors to handle liquids and a heating block to maintain temperatures, could be ready for use within a year because federal health agencies are fast-tracking diagnostics for Zika.
David O’Connor, a pathology professor at UW–Madison, said that while the technology is in the early stages, the concept is impressive.
“It needs to undergo significant refinement and optimization before it’s suitable for diagnostic use in a clinic,” he said. “But I think that people certainly are excited about the possibility of a simple test that can be used in resource-constrained settings.”
O’Connor is one of the scientists studying Zika in Indian rhesus macaques to try to answer some of the many questions surrounding the virus. The monkeys were infected with the Zika virus from a patient in French Polynesia. It is the same virus now circulating in South America.
The research began some months after some of O’Connor collaborators in Brazil shared growing concerns last year about a new Zika outbreak in the northern part of the country, he said.
“What we’re trying to do is rapidly address questions that take a lot longer to address in people,” O’Connor explained. “For example: what happens during pregnancy that causes some women to have babies with microcephaly and other abnormalities?
“What sort of immune response gets mounted against the virus and is this immune response sufficient to protect monkeys from being re-infected?” O’Connor said. “This is really important because we need to know if we make a vaccine are we going to have confidence that it’s going to be able to stop someone from being infected once they’ve received the vaccine.”
He expects the scientific community studying Zika to make meaningful strides in the coming months.
“By this time next year we’re going to have a much better handle on the situation and the best way to combat it,” O’Connor said of the disease.
Lourdes Medrano is a freelance journalist based in southern Arizona. Follow her on Twitter: @_lourdesmedrano