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US Public Health Laboratories Prepare Zika Virus Dx Strategy as Infections Increase

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NEW YORK (GenomeWeb) – As US officials continue to report new cases of Zika virus infections, the nation's public health laboratories are prepared with diagnostic tests and guidelines should the volume of suspected cases rapidly escalate, according to sources interviewed by GenomeWeb.

Capitalizing on funding and US Food and Drug Administration Emergency Use Authorizations, public laboratories are preparing with molecular- and antibody-based diagnostic tests. Meanwhile, diagnostic test manufacturers as well as the US Centers for Disease Control and Prevention are providing education about what kind of tests to have available, and how and when to use them. 

"We started to gear up and respond in January, when we first learned about travelers returning with the potential of having Zika virus," Kelly Wroblewski, director of infectious diseases at the Association of Public Health Laboratories in Silver Spring, Maryland, told GenomeWeb. APHL's membership includes state and local public health, environmental and agricultural laboratories, as well as companies. "Very rapidly, public health laboratories started to implement laboratory-developed tests, molecular assays primarily, to perform PCR testing that would identify active, acute infections."

In February and March, the FDA cleared two CDC assays under Emergency Use Authorizations. The first was the CDC Zika IgM Antibody Capture Enzyme-Linked Immunosorbent Assay, or Zika MAC-ELISA. Laboratory staff use it to detect Zika virus-specific IgM in human sera or cerebrospinal fluid that's submitted alongside a patient-matched serum specimen and meets CDC Zika virus clinical criteria or CDC Zika virus epidemiological criteria, or both. According to the CDC, anti-Zika IgM is typically detectable starting soon after the onset of symptoms and for about 12 weeks after infection. 

The second diagnostic test to receive the EUA was the CDC's Trioplex, a real-time RT-PCR assay used for the qualitative detection and differentiation of RNA from Zika virus, dengue virus, and chikungunya virus in human sera or cerebrospinal fluid.

Besides having PCR-based tests available, the majority of public laboratories — except some laboratories in the Northern United States, such as Alaska and North Dakota, where the risk of Zika transmission is low relative to other states — are also ready to perform the MAC-ELISA test, Wroblewski said. 

"The MAC-ELISA is a very labor-intensive assay with low throughput, and it's not automated at this point," Wroblewski added. "It just wasn't worth the time and the devotion of resources to implement it in the very far North. On the other hand, there are also a good number of local laboratories in Texas and California where the risk of transmission is higher and they have implemented the PCR and the ELISA assay."

Local laboratories, which are operated under the authority of US county or city governments, are relatively large in bigger cities and counties, such as in New York City and Los Angeles County, and they generally have both types of assays.

Since March, a range of Zika tests have received EUAs. As reported by GenomeWeb, tests developed by Viracor-IBT, Hologic, Altona Diagnostics, and Quest Diagnostics have all received the EUA label. Ubiquitome is also developing Zika tests with an application for EUA in mind.

Just this week, Siemens Healthcare Diagnostics became the most recent company to announce that the FDA has granted an EUA for its real-time PCR Zika virus assay.

"When Hologic was able to work in partnership with the FDA to gain emergency use authorization for the Aptima Zika test, it was an opportunity to have more available testing for patients," Edward Evantash, medical director and vice president of medical affairs at Hologic, told GenomeWeb.

The placement of so many of Hologic's Panther platforms around the US, especially in public health laboratories, creates a broad base for patients to have Zika testing completed in a timely fashion, he said.

The Panther system is available in all 50 states of the US and its territories, including Puerto Rico, he added.  "Panthers are used for sexually transmitted infection testing in over 90 percent of public health labs in the United States," he said. "So having that available now for Zika testing is great for patients and their physicians."

In addition to the Aptima Zika test, Hologic also has a test available, the Procleix assay, for blood bank screening for Zika, which the firm developed as part of a partnership with Grifols. The Grifols Procleix assays are built on amplification and detection technologies developed by Hologic, including target capture and transcription-mediated amplification.

OneBlood, a non-profit organization that provides blood to hospitals throughout most of Florida, is using a PCR assay from Roche running on the Cobas 8800 and 6800 test platforms, German Leparc, a senior medical consultant with OneBlood, told GenomeWeb.

In March, Roche received FDA approval to initiate collection and testing of blood samples for screening with the Cobas Zika assay under an Investigational New Drug Application protocol. That test is a qualitative in vitro nucleic acid screening test for the direct detection of Zika virus RNA in plasma specimens from human blood donors.

"We started testing on April 1," Leparc said. "As the mosquito season ramps up and we have local outbreaks in the state of Florida, we can use this high-throughput machine."  

For screening of blood donations, it is critical to have two instruments available in case one goes down. OneBlood has been testing samples from Puerto Rico, where Zika has been particularly impactful from an infection standpoint with 4,666 laboratory-confirmed, locally acquired virus disease cases as of the end of July, according to CDC.

Beginning this month, the organization will test samples collected in regions as they become active in the state of Florida, and it will also test samples for epidemiologic surveillance in an effort to detect outbreaks in regions before public health authorities declare they are active.

There are differences in the way blood donation centers screen for Zika virus versus how state and local laboratories operate. "In blood donation, you err on the side of sensitivity over specificity," Wroblewski said. "I'm not commenting on the capabilities of these tests, but that's generally how you would design a blood donation test as opposed to a diagnostic test."

In July, the CDC announced that it will begin awarding funds of nearly $60 million to states, cities, and territories to support efforts "to protect Americans from Zika virus disease and adverse health outcomes that can result from Zika infection." Meanwhile, the US Congress failed to pass legislation to provide $1.1 billion in funding for Zika prevention measures before taking its summer recess — though some legislators have called on their colleagues to return to Washington to address what they see as a growing crisis.

The CDC also recently issued updated interim guidelines concerning testing of pregnant women with possible exposure to the Zika virus. The guidelines recommend that serum and urine from all pregnant women with Zika symptoms be tested using RT-qPCR assays up to two weeks after symptom onset.

As of mid-July, 400 pregnant women in the US and District of Columbia and 378 pregnant women in all other US territories had received laboratory evidence of confirmed or possible Zika infection.  

The CDC's Interim Response Plan calls for increasing capacity for laboratory diagnostics, developing a laboratory surge capacity plan, streamlining procedures and confirmatory testing of suspect cases, and considering new laboratory tools that will reduce testing times. According to the plan, CDC's Laboratory Response Network, a national network of more than 150 laboratories, can process and test specimens in coordination with the CDC to manage laboratory surge efforts and address increased testing requirements.

According to the CDC, real-time reverse transcription-polymerase chain reaction (rRT-PCR) confirms Zika infection, can be performed rapidly, and is highly specific. Serum and urine samples for rRT-PCR testing should be collected as soon as possible after illness onset and within 14 days of onset, the CDC said.

In the past couple of weeks, laboratories began receiving notices of the receipt of new Zika funds from funding entities such as CDC, Wroblewski said. "The funds, in general, will be applied during August," she said.

Laboratories apply for funds by justifying the need and explaining how they will apply money that's been awarded to them. "For Zika, you have reagents and equipment, but most of the funding is likely to be spent on staff. … Funding is particularly needed to do non-automated or manual serology," Wroblewski said.

When it comes to diagnostics, the availability of the right kinds of tests is one important aspect of Zika readiness. Educating people who work in labs is another key element, according to Hologic's Evantash. "There's a lot of uncertainty around Zika testing and the risk to pregnant women. Our goal is to educate the labs on how to do testing appropriately, and also making sure that physicians know that they are getting the right test and doing the test correctly both in terms of collection and follow up."

The monetary benefit to companies providing Zika diagnostic tests is expected to be limited, according to industry analysts and chief executives of companies providing testing equipment, but diagnostics company executives have said they see the supply of Zika tests as an opportunity to prove their capabilities related to quickly gearing up to support a coordinated response to the threat provided by a global health risk.

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