Category Archives: Coronavirus

Do Antibody Infusions Work Against COVID-19?

artist rendition of coronavirus
See the spikes? Or are they golf tees?

A monoclonal antibody given to patients with mild COVID-19 reduced symptom severity and the odds of needing hospitalization.

About 10 days ago the hospital where I work started giving intravenous antibodies to COVID-19 patients in the emergency department. These are folks with COVID-19 symptoms and a positive COVID PCR test within the last three days but they’re not sick enough to warrant admission. My impression is that the infusion is monoclonal antibodies, different from the convalescent plasma we were offering to inpatients several months ago.

The antibody used in the study at hand is “LY-CoV555 (also known as LY3819253), a potent antispike neutralizing monoclonal antibody that binds with high affinity to the receptor-binding domain of SARS-CoV-2,” and “was derived from convalescent plasma obtained from a patient with Covid-19.” I assume scientists figured out a way to synthesize that antibody in a lab.

Click on Abstract for full details.



Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (Covid-19), which is most frequently mild yet can be severe and life-threatening. Virus-neutralizing monoclonal antibodies are predicted to reduce viral load, ameliorate symptoms, and prevent hospitalization.

This was a very small study; only a little over a hundred patients in each of three treatment groups (three different doses) and the placebo group.


In this ongoing phase 2 trial involving outpatients with recently diagnosed mild or moderate Covid-19, we randomly assigned 452 patients to receive a single intravenous infusion of neutralizing antibody LY-CoV555 in one of three doses (700 mg, 2800 mg, or 7000 mg) or placebo and evaluated the quantitative virologic end points and clinical outcomes. The primary outcome was the change from baseline in the viral load at day 11. The results of a preplanned interim analysis as of September 5, 2020, are reported here.


At the time of the interim analysis, the observed mean decrease from baseline in the log viral load for the entire population was −3.81, for an elimination of more than 99.97% of viral RNA. For patients who received the 2800-mg dose of LY-CoV555, the difference from placebo in the decrease from baseline was −0.53 (95% confidence interval [CI], −0.98 to −0.08; P=0.02), for a viral load that was lower by a factor of 3.4. Smaller differences from placebo in the change from baseline were observed among the patients who received the 700-mg dose (−0.20; 95% CI, −0.66 to 0.25; P=0.38) or the 7000-mg dose (0.09; 95% CI, −0.37 to 0.55; P=0.70). On days 2 to 6, the patients who received LY-CoV555 had a slightly lower severity of symptoms than those who received placebo. The percentage of patients who had a Covid-19–related hospitalization or visit to an emergency department was 1.6% in the LY-CoV555 group and 6.3% in the placebo group.


In this interim analysis of a phase 2 trial, one of three doses of neutralizing antibody LY-CoV555 appeared to accelerate the natural decline in viral load over time, whereas the other doses had not by day 11. (Funded by Eli Lilly; BLAZE-1 number, NCT04427501. opens in new tab

Another study looked at the use of a cocktail containing two monoclonal antibodies in non-hospitalized patients. Researchers concluded:

In this interim analysis, the REGN-COV2 antibody cocktail reduced viral load, with a greater effect in patients whose immune response had not yet been initiated or who had a high viral load at baseline. Safety outcomes were similar in the combined REGN-COV2 dose groups and the placebo group. (Funded by Regeneron Pharmaceuticals and the Biomedical and Advanced Research and Development Authority of the Department of Health and Human Services; number, NCT04425629. opens in new tab.)

Click for details.

Their report indicated that those who received the antibodies were less likely to need subsequent medical visits. But they didn’t put that in their concluding paragraph so I will assume it didn’t reach statistical significance.

Neither of these studies reported reduction in death rates.

+ + +

Obesity, particularly BMI 35 or higher, is risk factor for serious COVID-19 disease. If obese, you’ve had almost a year to work on it. How ya doin’? I can help if needed. See the book below.

Steve Parker, M.D.

What About Melatonin for COVID-19?

Photo by Anna Shvets on

Melatonin is a commonly-available over-the-counter sleep aid. In 2020, the Cleveland Clinic did epidemiological study that linked melatonin usage with a 30% reduced risk of contracting COVID-19. Clinical psychologist Michael J Breus, Ph D has an article at Psychology Today on the use of melatonin as a preventative or treatment for COVID-19.

Melatonin, of course, is best known as a sleep regulator. But melatonin also plays an important role in regulating the immune system. One way it does so is by influencing the production of small proteins known as cytokines, which act as signalers from the immune system to cells around the body. Cytokines can be inflammation producing (pro-inflammatory cytokines) or inflammation restricting (anti-inflammatory cytokines). Melatonin has been shown to reduce the production of pro-inflammatory cytokines. Melatonin also is well known to be an antioxidant, neutralizing free radical cells and limiting oxidative stress and damage, which contribute inflammation.

Pro-inflammatory cytokines serve an important purpose, in marshaling the inflammatory response that fights off viruses, bacteria, and other pathogens. That’s the protective mechanism of inflammation at work. But for the pro-inflammatory cytokine response to be beneficial, it must be proportional to the threat. A too vigorous response of pro-inflammatory cytokines creates a dangerous amount of inflammation—and can actually serve to spread the viral infection, rather than tamping it down. It is this inflammatory overreaction and viral spread that appears to take place in the most serious cases of COVID-19.

I spent 10 minutes on the Internet trying to find the appropriate dose of melatonin for its possible preventative and treatment powers. But no luck. It’s likely in the range of 1 to 10 mg/day, typically taken at night or bedtime. For insomnia in my hospitalized patients, I start at 1.5 mg. Most of my colleagues use a much higher dose. Dr Josh Farkas at suggests that the treatment dose is 5 mg/day.

As always, check with your personal physician first.

Steve Parker, M.D.

Does Remdesivir Help Fight COVID-19?

intubation, mechanical ventilation, ventilator
Intubated to prevent death

Remdesivir and hydroxychloroquine don’t do much good for hospitalized COVID-19 patients, according to this abstract of the SOLIDARITY trial:


World Health Organization expert groups recommended mortality trials of four repurposed antiviral drugs — remdesivir, hydroxychloroquine, lopinavir, and interferon beta-1a — in patients hospitalized with coronavirus disease 2019 (Covid-19).


We randomly assigned inpatients with Covid-19 equally between one of the trial drug regimens that was locally available and open control (up to five options, four active and the local standard of care). The intention-to-treat primary analyses examined in-hospital mortality in the four pairwise comparisons of each trial drug and its control (drug available but patient assigned to the same care without that drug). Rate ratios for death were calculated with stratification according to age and status regarding mechanical ventilation at trial entry.


At 405 hospitals in 30 countries, 11,330 adults underwent randomization; 2750 were assigned to receive remdesivir, 954 to hydroxychloroquine, 1411 to lopinavir (without interferon), 2063 to interferon (including 651 to interferon plus lopinavir), and 4088 to no trial drug. Adherence was 94 to 96% midway through treatment, with 2 to 6% crossover. In total, 1253 deaths were reported (median day of death, day 8; interquartile range, 4 to 14). The Kaplan–Meier 28-day mortality was 11.8% (39.0% if the patient was already receiving ventilation at randomization and 9.5% otherwise). Death occurred in 301 of 2743 patients receiving remdesivir and in 303 of 2708 receiving its control (rate ratio, 0.95; 95% confidence interval [CI], 0.81 to 1.11; P=0.50), in 104 of 947 patients receiving hydroxychloroquine and in 84 of 906 receiving its control (rate ratio, 1.19; 95% CI, 0.89 to 1.59; P=0.23), in 148 of 1399 patients receiving lopinavir and in 146 of 1372 receiving its control (rate ratio, 1.00; 95% CI, 0.79 to 1.25; P=0.97), and in 243 of 2050 patients receiving interferon and in 216 of 2050 receiving its control (rate ratio, 1.16; 95% CI, 0.96 to 1.39; P=0.11). No drug definitely reduced mortality, overall or in any subgroup, or reduced initiation of ventilation or hospitalization duration.


These remdesivir, hydroxychloroquine, lopinavir, and interferon regimens had little or no effect on hospitalized patients with Covid-19, as indicated by overall mortality, initiation of ventilation, and duration of hospital stay.

Steve Parker, M.D.

From the UK: More COVID-19 Vaccine Skepticism

face mask, elderly, worried
Very few, if any, vaccine trial participants were elderly and carrying major co-morbidities

UK Medical Freedom Alliance has published a white paper on the new vaccines:

The morbidity and mortality impact on public health from SARS-CoV-2 must be balanced with the risks and costs of a vaccine roll-out. We have shown that the mortality and morbidity from SARS-CoV-2 is no longer an existential threat to society.

It is a huge responsibility to roll out a vaccine manufactured with novel technology. To do so with the intention that all 60+ million people in the UK should receive the vaccine as soon as possible, without full transparency as to potential risks, may be viewed as irresponsible, potentially even negligent, from a legal standpoint. We urge you to heed the wisdom in the Hippocratic Oath: “First, do no harm“.

The only alliance team member I’ve heard of is Dr Malcolm Kendrick. I’m sure none of them have ever heard of me.

I haven’t decided what I’ll tell my my mother if she asks me if she should take the vaccine soon. She’s 89 years old and readily admits she’s ready to go to Heaven. What has she got to lose? I’ll back her choice either way.

Steve Parker, M.D.

Ivermectin for COVID-19?

face mask, young woman
Probably at little risk of serious illness if she’s generally healthy

From Diabetes Metab Syndr in Sept 2020:

The clinical efficacy and utility of ivermectin in SARS CoV-2 infected patients are unpredictable at this stage, as we are dealing with a completely novel virus. However, repurposing existing drugs as possible COVID-19 treatment is astute usage of existing resources, and we await results of well-designed large scale randomized controlled clinical trials exploring treatment efficacy of ivermectin to treat SARS-CoV-2.

The authors of this letter mention current clinical trials (~38) with a dose [presumably by mouth] ranging from 200 to 1200 mcg/kg body weight, for a duration of 3–7 days, which is showing promising results both in terms of symptoms as well as viral load reduction. Another article mentioned the usual treatment dose is 0.2mg/kg on day 1 and day 3 followed by Days 6 and 8 if not recovered.

The authors cite the Broward Health hospital system study from South Florida. In this small pilot study, hospitalized patients treated with ivermectin had a better survival rate compared with “standard care,” whatever that was back in Spring 2020. The ivermectin-treated patients received “at least one dose” of the drug at 200 mcg/kg, by mouth. Has this report been peer-reviewed and published yet? If not, why not?

Moving on…

One small study (probably 60 each in the treatment and placebo groups) found that 12 mg ivermectin by mouth once a month impressively protected healthcare workers against COVID-19.

Another study: “Two-dose ivermectin prophylaxis at a dose of 300 μg/kg with a gap of 72 hours was associated 73% reduction of COVID-19 infection among [hospital] healthcare workers for the following one-month. Further research is required before its large scale use.”

After hydroxychloroquine, azithromycin, and ivermectin, will nitazoxanide be the next panacea? You heard it first here!

A small study in Barcelona found no benefit from a single standard dose (200 mcg/kg) of ivermectin in patients hospitalized with severe disease. They suggest that a higher dose might be useful.

I’ve spent about 90 minutes on my day off trying to figure out if I should prescribe ivermectin to my hospitalized patients. My conclusion is that we need more and better data before it’s ready for prime time. I agree with Dr Ananda Swaminathan, who probably spent many hours more on the subject:

Evidence for the use of Ivermectin is based on in vitro [lab studies, not living animals], prophylaxis, clinical, safety, and large-scale epidemiologic studies (heterogenous populations in multiple different settings) BUT…

Many of the trials thus far are methodologically flawed without enough information about baseline demographics, multiple primary outcomes, soft/subjective outcomes, convenience samples, and unclear definitions, just to name a few

Additionally, a valid concern in evaluating the literature is that many of the trials have not yet passed the peer review process and are in pre-print format

Although Ivermectin is cheap, readily available, with a fairly safe side effect profile, based on the evaluation of the literature above, at this time, Ivermectin should not be recommended outside of a clinical trial to ensure we get a true answer of effect

Ivermectin is interesting, there is certainly signal to evaluate further, but in our desire to want a treatment option, let’s not continue to do the same thing over and over again, as we saw play out with Hydroxychloroquine

Like they say, “more studies are needed.”

Steve Parker, M.D.

PS: Something you can do to help prevent and survive COVID-19 is to get and stay as healthy as possible. Let me help:

Where Do You Go For Satisfaction After Injury by the New COVID-19 Vaccine?

No, you won’t have to inject the vaccine yourself

I know it’s a little early to be asking that question. Within a year, an unknown number of you will be asking. Where do you go for satisfaction? The “National Vaccine Injury Compensation Program.” Forget about suing the vaccine manufacturer, distributor, or medical practitioner who jabbed you. They got the federal government to absolve them of liability in most cases.

As far as I know, this program only applies to U.S. residents. Perhaps only U.S. citizens.

The following is verbatim from the NVICP web page, not my words:

Vaccines save lives by preventing disease.

Most people who get vaccines have no serious problems. Vaccines, like any medicines, can cause side effects, but most are very rare and very mild. Some health problems that follow vaccinations are not caused by vaccines.

In very rare cases, a vaccine can cause a serious problem, such as a severe allergic reaction.  

In these instances, the National Vaccine Injury Compensation Program (VICP) may provide financial compensation to individuals who file a petition and are found to have been injured by a VICP-covered vaccine. Even in cases in which such a finding is not made, petitioners may receive compensation through a settlement. 

How does the VICP work?

The National Vaccine Injury Compensation Program is a no-fault alternative to the traditional legal system for resolving vaccine injury petitions.

It was created in the 1980s, after lawsuits against vaccine companies and health care providers threatened to cause vaccine shortages and reduce U.S. vaccination rates, which could have caused a resurgence of vaccine preventable diseases.

Any individual, of any age, who received a covered vaccine and believes he or she was injured as a result, can file a petition. Parents, legal guardians and legal representatives can file on behalf of children, disabled adults, and individuals who are deceased.

What is the process?

  1. An individual files a petition with the U.S. Court of Federal Claims.
  2. The U.S. Department of Health and Human Services medical staff reviews the petition, determines if it meets the medical criteria for compensation and makes a preliminary recommendation.
  3. The U.S. Department of Justice develops a report that includes the medical recommendation and legal analysis and submits it to the Court.
  4. The report is presented to a court-appointed special master, who decides whether the petitioner should be compensated, often after holding a hearing in which both parties can present evidence. If compensation is awarded, the special master determines the amount and type of compensation.
  5. The Court orders the U.S. Department of Health and Human Services to award compensation. Even if the petition is dismissed, if certain requirements are met, the Court may order the Department to pay attorneys’ fees and costs. 

The special master’s decision may be appealed and petitioners who reject the decision of the court (or withdraw their petitions within certain timelines) may file a claim in civil court against the vaccine company and/or the health care provider who administered the vaccine.

Parker here again. I’d never heard of a “special master” before. Makes me think you’re a slave when you enter the system. I searched the “covered vaccines” but didn’t see the COVID-19 vaccines. But I bet they’re covered.

Don’t label me as anti-vaccine in general. I am not. As a child I got the vaccines for polio, measles, mumps, rubella, tetanus, and probably diphtheria, maybe others. I took the hepatitis B vaccine as an adult because I’m exposed to blood from my patients. I’m due for another tetanus booster and will take it without reservation.

I’ve got risk factors for more serious COVID-19 disease: age 66 and hypertension. After reviewing what little data are available from the Warp Speed vaccine trials, I’m not convinced the vaccines are safe enough for me. I’ll take my chances with the virus rather than the vaccine. I’m not afraid of dying from COVID-19; if that happens I’ll be in heaven with Jesus. I’ve lived a full and lucky life, blessed by a wonderful wife, fantastic children, good health, missed Viet Nam by a few years, no major economic upheaval. My biggest concern about catching the virus is the burden it would lay on my co-workers if I’m off-duty for 1 to 3 weeks.

That said, if I were older and had other co-morbidities, I might take the vaccine now. When we have more long-term data on vaccine safety, I might take the vaccine. It could take up to a couple years before we have that data.

Steve Parker, M.D.

PS: I’m doing everything I can to optimize my health and immune system, including weight management and regular exercise.

Update on Dec 11, 2020:

Pharmacist Scott Gavura at Science Based Medicine provides a table comparing vaccination vs catching the virus vs hydroxychloroquine treatment. He implies my odds of death from COVID-19 infection are two out of a hundred (2%). I don’t think it’s nearly that high.

Update on Dec 17, 2020:

I’m wrong about the NVICP compensating you financially if injured but the current COVID-19 vaccines. The correct program seems to be the CICP: Countermeasures Injury Compensation Program. File your claim within a year of vaccination.

Click for an interesting article on CICP at the Centre for Research on Globalization. I have no idea of its accuracy.

CA Filipino Nurses in Hospitals Disproportionately Affected By #COVID19 #Coronavirus

hospital emergency room
New York Governor Cuomo was sending COVID-19 patients to nursing homes from the hospital, to help spread the infection, I guess.
<p class="has-drop-cap" value="<amp-fit-text layout="fixed-height" min-font-size="6" max-font-size="72" height="80">I work with and respect,many Filipino hospital nurses in Arizona. I wonder what % of California hospital nurses are Filipino. I figure there are federal government programs that facilitate immigration of Filipino nurses to the U.S.I work with and respect,many Filipino hospital nurses in Arizona. I wonder what % of California hospital nurses are Filipino. I figure there are federal government programs that facilitate immigration of Filipino nurses to the U.S.

Filipino nurses in particular were found, as of September, to represent a third of the nursing population’s COVID-19 deaths, despite only making up 4% of all nurses in the United States. National Nurses United believes the death count has gone up since then.

A report release in September by National Nurses United, the country’s largest nurses union, found that California is leading in COVID-19 infection rates amongst health care workers nationwide. The Golden State reported 35,525 infection cases, followed by Georgia at 17,317, then Florida at 16,380. California ranks third in overall health care worker deaths, behind New York and New Jersey.

“A lot of Filipino nurses hold bedside positions,” explained Elizabeth West, a Sacramento registered nurse of Filipino decent who became infected with COVID-19. “We are right next to the patient when they get intubated… when they go into cardiac arrest… we are the first ones there.”

Source: Study: California leads in health care worker COVID-19 infections

Steve Parker, M.D.

Vitamin D Seems to Play a Role in Preventing Severe Illness and Death From #COVID19 #Coronavirus

intubation, mechanical ventilation, ventilator
If you have to be on a life-support breathing machine (ventilator), this qualifies as severe COVID-19 disease. Ventilator is at the bedside out of the picture. To tolerate the tube in your throat, you’ll be in the “medically-induced coma” you read about in the news.

From Northwestern Now:

After studying global data from the novel coronavirus (COVID-19) pandemic, researchers have discovered a strong correlation between severe vitamin D deficiency [based on blood levels] and mortality rates.

Led by Northwestern University, the research team conducted a statistical analysis of data from hospitals and clinics across China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the United Kingdom (UK) and the United States.

The researchers noted that patients from countries with high COVID-19 mortality rates, such as Italy, Spain and the UK, had lower levels of vitamin D compared to patients in countries that were not as severely affected.

Our bodies have two source of vitamin D. Our skin can make it if given sufficient exposure to sunlight, or we can ingest it. Many folks don’t swallow and/or absorb enough of it, or don’t get enough sun exposure.

I’ve never been to Europe and readily confess I don’t know much about it. I figured the UK doesn’t get much sunlight, but Spain and Italy do (at least southern Italy). Maybe the heavy air pollution in northern Italy—e.g., Lombardi—blocks out the sun.

trees, forest, sunlight
Not a lot of sunlight penetrating through this forest

The researchers say that vitamin D keeps the immune system from over-reacting to the virus infection. A hyperactive immune system response causes widespread inflammation, which in turn damages various body tissues, leading to severe illness and sometimes death. This is the “cytokine storm” you may have heard about. That’s the theory anyway.

I never knew vitamin D was involved in the immune system, or if I did, I forgot. Like most physicians, my interest in vitamin D relates to calcium metabolism and bone health/fracture prevention.

Professor Backman is quoted in the article:

It is hard to say which dose [of vitamin D supplement] is most beneficial for COVID-19,” Backman said. “However, it is clear that vitamin D deficiency is harmful, and it can be easily addressed with appropriate supplementation. This might be another key to helping protect vulnerable populations, such as African-American and elderly patients, who have a prevalence of vitamin D deficiency.

Clicking this link may take you to the prepublication original research report.

A few days ago, CNN reported that black people are four times more likely to die from COVID-19 than are whites. Here in the U.S., we’ve seen disproportionately high fatalities among blacks living in Chicago, New Orleans, and Milwaukee County, Milwaukee. I’m not the first to wonder if vitamin D deficiency is a contributing factor. I mentioned earlier that our skin makes vitamin D when exposed to sufficient sunlight. But that process is less efficient in darker skin. And folks at more northern latitudes tend to get less sun exposure, particularly in winter. (Lack of sunlight shouldn’t be a problem in New Orleans). We’ve know for years that U.S. blacks have “sub-optimal” vitamin D blood levels. Click for even more reading on this issue if you’re crazy; it’s complicated. Despite low blood levels of 25-hydroxyvitamin D, blacks are not prone to thin-bone osteoporotic fractures like whites and east asians. Some experts suggest that higher rates of diabetes and hypertension in U.S. blacks is related to low vitamin D levels.

What we don’t know is:

  • If you have COVID-19 and try to augment your vitamin D level with a supplement, will you have a better outcome?
  • If you are deficient in vitamin D now but take measures to raise your blood level (via food or supplementation), will you be less likely to contract COVID-19 and able to avoid serious illness if you do get sick?
  • Would the answers to the first two questions depend on whether you have black, brown, white, pink, or polka-dotted skin?

Hey, doc. Tell me something concrete I can do now to improve my odds of surviving this pandemic!

If you’re black of otherwise dark-skinned, I don’t know what to tell you.

If you qualify as a vulnerable person, why not ask your doctor to order a vitamin D blood level (called 25-OH-vitamin D)? If that’s not possible, ask your doc if 1,000 units of vitamin D3/day (cholecalciferol) by mouth is a good idea.

     Steve Parker, M.D.

PS: About a week ago I ran across a study finding that pre-sickness use of vitamin D supplements was linked to worse outcomes in COVID-19. I tried to find it a few days later but couldn’t. I’m sorry if this perplexes you. Welcome to the scientific literature and nature of medical practice.

Face masks: Panacea or Poppycock? #COVID19

face mask, young woman
If she got the ‘rona, her mask my protect YOU, whether or not you wear a mask

Here’s an excerpt from the recent Danish study that questions the efficacy of facemarks in preventing transmission of SARS-CoV-2 virus. Note that there were ~3,000 folks in both the experimental and control groups. The experimental group wore surgical masks, so this study says nothing about cloth masks, N95s, or bandanas. Also note this study was done at at time early in the pandemic when mask-wearing by the public was not at all common, quite a bit different from today’s world in many places. The investigators suggest that for face masks to prevent transmission of the virus, the masks need to be worn by already-infected, viral-shedding people.

In this community-based, randomized controlled trial conducted in a setting where mask wearing was uncommon and was not among other recommended public health measures related to COVID-19, a recommendation to wear a surgical mask when outside the home among others did not reduce, at conventional levels of statistical significance, incident SARS-CoV-2 infection compared with no mask recommendation. We designed the study to detect a reduction in infection rate from 2% to 1%. Although no statistically significant difference in SARS-CoV-2 incidence was observed, the 95% CIs are compatible with a possible 46% reduction to 23% increase in infection among mask wearers. These findings do offer evidence about the degree of protection mask wearers can anticipate in a setting where others are not wearing masks and where other public health measures, including social distancing, are in effect. The findings, however, should not be used to conclude that a recommendation for everyone to wear masks in the community would not be effective in reducing SARS-CoV-2 infections, because the trial did not test the role of masks in source control of SARS-CoV-2 infection. During the study period, authorities did not recommend face mask use outside hospital settings and mask use was rare in community settings. This means that study participants’ exposure was overwhelmingly to persons not wearing masks.

Source: Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers: A Randomized Controlled Trial: Annals of Internal Medicine: Vol 0, No 0

Steve Parker, M.D.

Is a Patient With #COVID19 Infectious as Long as Their PCR Test Is Positive? #Coronavirus

artist's rendition of coronavirus
Artist’s rendition of Coronavirus

Investigators in the UK reviewed the literature of evidence on how long someone with COVID-19 remains infectious. Their answer: No longer than eight days after symptom onset. Source:

Viral cultures for COVID-19 infectivity assessment – a systematic review (Update 4) 

This is important to know because the PCR test for diagnosis of cases can remain positive for up to 83 days. Transmission of infection requires whole live virus – the more the better – not just the fragments of RNA that the PCR tests detect.

The best evidence for ongoing infectiousness is when virus from body fluids can be seen to grow in tissue cultures. Perhaps second best is when tissues or cell cultures are exposed to virus, and microscopic examination shows cell damage.

The commonly used clinical test of COVID-19 infection is called PCR (more accurately, reverse transcriptase polymerase chain reaction to RT-PCR). This test detects fragments of viral RNA, and amplifies them to make them easier to detect. The amount of amplification required for detection is called “cycle threshold” or Ct. If a lot of viral RNA is present, it doesn’t require much amplification. There are many different coronavirus tests on the market. If a test requires too much amplification (i.e., Ct is over 25-35), then it’s probably not a true positive test for SARS-CoV-2; it may be detecting RNA from some other coronavirus, or contamination. Interestingly, my patients have probably been tested with at least three or four different PCR tests over the last six months: the test reports I see never report their cycle threshold.

A false positive PCR test is one where the test is positive but the patient isn’t really infected. If you’re a government who wants a high “case” number, choose a test with a high Ct, over 30-35. (Again, it depends on the particular fragment of RNA being looked for, and other esoteric factors.)

The authors cited a couple cases of COVID-19 in which viral RNA was found in secretions at 78 and 83 days after initial diagnosis. They fully expect, however, that the RNA detected was viral debris, not whole infectious virus.

Remember, this is just one study. It hasn’t been peer-reviewed yet. We’re learning more as each month passes. Stay tuned.

Steve Parker, M.D.