COVID-19 testing

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aprilie 10, 2026

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aprilie 10, 2026

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"Several other tests are based on a technique called loop-mediated isothermal amplification (LAMP), which also works at a constant temperature and has been used to identify viruses such as Zika. LAMP relies on two enzymes — one to convert the viral RNA to DNA, and another to copy DNA — as well as a set of four to six short primers designed to recognize different snippets of the viral genome. These fragments not only help to get the copying started, as in RT-PCR, but also allow newly copied DNA strands to form looped structures that can be amplified much more rapidly than in standard PCR (see ‘Loop the loop’). It is less accurate, however, and only a few dozen samples can be run at a time. Because the technique doesn’t need special instruments, it can be used in the field and in regions that lack advanced equipment, including remote areas and refugee camps, says Vicent Pelechano, a genomics expert at the Karolinska Institute in Stockholm, who co-developed a LAMP-based assay for SARS-CoV-2. “All you need is a test tube containing the primers, a pipette, a hotplate and a pot of water,” he says. A single test would cost about $1 — not counting labour. In the lab, Pelechano and colleagues’ LAMP-based test could detect as few as 10 copies of a SARS-CoV-2 genome in no longer than 40 minutes1. The researchers then tested the assay using samples from 248 people with confirmed coronavirus infection, and could detect the virus nearly 90% of the time2. Pelechano acknowledges that the test might turn out to be less accurate for some samples, such as those contaminated with blood. But in some places, the trade-off in accuracy could be worth it. Low-income countries and war-torn areas don’t have enough PCR machines to perform the standard diagnostic test for coronavirus, says Nabil Karah, a clinical microbiologist at Umeå University in Sweden. Karah is working with other scientists and with Pelechano’s team to bring their LAMP-based test to Syria to increase local testing capacity."

- COVID-19 testing

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"Another way researchers are trying to bring testing to the masses is to devise assays that could be used in temporary testing facilities, drive-through testing centres and even in people’s homes. At least two teams are taking advantage of the gene-editing technology CRISPR to power such tests. For example, researchers led by Zhang have developed a coronavirus assay that can be run in a single test tube in about an hour4. But it still requires heating the sample to about 65 °C, and it’s not as sensitive as a PCR-based assay. “That’s okay, because it’s much easier to use,” Zhang says. When tested multiple times on samples from 12 people infected with coronavirus, the assay detected the virus on nearly every occasion. The test builds on an approach that Zhang co-developed in 2017, called SHERLOCK5, which relies on the ability of the CRISPR machinery to home in on specific genetic sequences. Researchers program a guide molecule to latch on to a particular stretch of the SARS-CoV-2 genome. If the guide molecule finds a match, a CRISPR enzyme generates a signal that can be detected either as a fluorescent glow or as a dark band on a paper dipstick (see ‘Cut and detect’). On 6 May, the US Food and Drug Administration (FDA) authorized a SHERLOCK coronavirus assay for emergency use. The test is made by biotechnology firm Sherlock BioSciences in Cambridge, Massachusetts (of which Zhang is a co-founder), and the company has partnered with a manufacturer to mass-produce the kits. (See also ‘Coronavirus assays assessed’.)"

- COVID-19 testing

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"Municipal wastewater is a composite biological sample of an entire community with each member of the community inputting biological specimens every day. It is therefore no surprise that wastewater has been tapped as an epidemiological tool to gauge aspects of public health, such as narcotic usage, the reemergence of poliovirus, and infection rates of viral and bacterial diseases. COVID-19 has accelerated the interest in wastewater-based epidemiology (WBE) due to the fact that SARS-CoV-2 genes are detected in the feces of many infected individuals. More established epidemiological tools used to track cases in a community have been hindered during the COVID-19 pandemic by diagnostic kit shortages, asymptomatic or mild cases that do not encounter the medical system or delay seeking medical attention, and the lag times between testing and reporting. As a result, public health officials and administrators have had to make critical decisions about opening or closing communities with limited surveillance data. Scientists, engineers, public officials, and the general public, are optimistic that WBE could provide additional data on COVID-19 infections in a community. In fact, the United States Center for Disease Control has established the National Wastewater Surveillance System as a framework for using WBE to inform the response to the COVID-19 pandemic. Recent published studies have reported SARS-CoV-2 detection and quantification in sewage. Based on these reports, numerous entities/organizations across the globe and across scales are moving to implement WBE. It remains to be seen how the data generated from wastewater surveillance should be interpreted or will ultimately be used to make public health decisions. Potential uses include informing on the presence or absence of COVID-19 in a community, similar to polio surveillance; tracking trends over time to project infection trajectory in the coming days; or even using the SARS-CoV-2 concentrations in wastewater to estimate prevalence in a community. The latter application requires a clear understanding of fecal shedding dynamics over the course of the illness, which is not yet established."

- COVID-19 testing

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