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The Centers for Disease Control and Prevention is developing tests that could provide public health officials crucial information about how broadly the coronavirus has spread in the United States, even among mild cases or people without symptoms, the agency’s director said Wednesday.

The serologic tests, which are different from the ones used to diagnose active infection, would allow researchers to test the blood of people who were not confirmed cases of Covid-19 in communities where the virus spread. They would be designed to look for signs that people have mounted an immune response after being exposed to the virus.


CDC Director Robert Redfield told Congress that the agency is working on two of these types of tests. “CDC has developed two serological tests that we’re evaluating right now so we can get an idea through surveillance what’s the extent of this outbreak, how many people really are infected,” he told a House panel. “That is being moved out now to do these extensive surveillance programs.”

Understanding the full scope of an outbreak would allow authorities to learn more about how the virus spreads. It would also provide a more accurate picture of the so-called infection fatality ratio, or, in layman’s terms, the percentage of cases that are fatal. The figure is arrived at by taking the number of deaths and dividing that by the number of cases, so if many thousands of cases are not accounted for, it can make a disease appear more lethal than it actually is.

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Researchers in China and Singapore have also developed serologic tests and have initiated these types of studies, according to the World Health Organization. The agency has called on all countries with cases to conduct this kind of epidemiological work.


“These types of studies should be conducted now,” Maria Van Kerkhove, who heads WHO’s emerging diseases and zoonoses unit, recently told STAT. “This is one of the major things that needs to be done now. And everywhere. Not just in China. In the U.S., in Italy, in Iran — that would give us a better understanding of where this virus is and if we’re truly missing a large number of cases.”

She added: “Until we have population-based sero-surveys, we really don’t truly know.”

At a press briefing in Geneva Wednesday, Van Kerkhove called for the public sharing of the results from serologic studies and said the WHO hopes to have some data in the coming weeks from China.

“It will take some time,” she said. “We do need to give them the time to run these sero-epi investigations.”

  • I think I may have had it, too. We were on vacation at Orlando theme parks in late January, returning home to PA on the 25th. On the 27th, I woke up in the wee hours with an itch deep in my lungs, and had a terrible dry cough, chills, 102 fever, terrible headache and hurt all over by by noon of that day. Fever continued 4-5 days, despite lots of ibuprofen, by which time I also had some head congestion. Painful cough persisted for over a week, but never became productive. And never much nasal drainage either, despite the sinus pain and congestion. Never did develop shortness of breath, though just walking out to get the paper late that first week sent me back to bed for the day! Finally started feeling better the following week, but incredibly weak and tired all the time. Went to see my family Dr. early the second week, where a swab for influenza was negative, After two full weeks was pretty good. But this felt like the worst flu I’d had since childhood. I would say the most distinctive feature of the whole illness was the dry cough, which they say is characteristic of Covid-19. I have seen a story fro China where researchers suggested that there may have been an earlier, less aggressive strain circulating before the Wuhan outbreak exploded. If not Covid-19, maybe I had that??

    I’m mid 60s and diabetic and afraid to do anything but hunker down, as instructed. Sure wish I knew whether I had immunity, so I could try to get out and help my local community with food deliveries or something instead of just laying low.

  • Researchers in China and Singapore have also developed serologic tests and have initiated these types of studies, according to the World Health Organization.

    Gee I thought US was by far the most advanced country in the world for this type of matter. Clearly it seems not. How much longer to complete development and deploy thee tests? Weeks, months? Disappointing and graceful….

  • Many people have already had it. Would be nice if this Covid-19 antibody test was more widely available:

    Available under an emergency FDA ruling. The CDC would be well advised to use existing tests, even if they wanted to do additional validation, than to try and invent something that already exists. Disinclination to use the WHO covid-19 test, preferring to develop a new one already set US testing back once.

  • I was diagnosed with pneumonia on January 5 and I was sick until January 21. I started with a sore throat on Dec. 30 and went in for a horrendous cough on January 3. Ended up in ER January 5 with a worse cough, horrible wheezing, and slept only 9 hours in 72 hours because of my constant coughing and wheezing. CT scan showed pneumonia in upper and lower right lobe and I was on a nebulizer for 10 days. My cough was so bad I broke a rib . I finally started feeling well enough to go to work on January 20th but really didn’t feel 100% better until the first week of February. Definitely interested in taking a serologic test when available.

  • I live in Washington County in Oregon, just outside Portland. There have been cases in Washington County. On Feb. 13, I came down with body aches, sore throat, fever and chills for two days, with a quick onset of a dry cough that lasted almost two weeks. I was up and about on day three. Nine days after my my symptoms appeared, my 20 year old son got the exact same symptoms. In the meantime (before he became symptomatic) we had flown to the Caribbean, passing through five airports.

    • My family and I traveled internationally from Florida to Canada from 1/3-1/11. We passed through 3 airports on the way there and 3 on the way back. On 1/11 my daughter (15) and I (49) developed sore throat, cough, high fevers 103.5 plus, decreased appetite, weight loss. I am in overall great health and figured it was viral and it will pass. It did not. The fevers lasted for 4 days despite alternating ibuprofen and acetominophen. The cough was relentless despite chest PT, inhalers, moist air, you name it. The body aches- debilitating. Mentally it was also also very confusing- couldn’t focus on the simplest task. My husband (49), also in great health, developed the same symptoms 3 days later. The cough, the shortness of breath, the decreased appetite and general feeling like death lasted for 6 weeks. We are just starting to turn a corner. This was by far one of the worst infections I had ever had and being a physician around sick patients for the past 20 plus years- I have nearly had them all! Sign me up for serological testing. It will be one of the only sure ways epidemiolgically to get a grasp on how widespread this virus already is and will be.

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