As businesses and groups fluctuate between gathering or not, many have taken to doing a symptom check in the hope of reducing exposure to SARS-CoV-2. This usually consists of asking several questions, such as whether you have been exposed to anyone with an active infection or if you’ve had symptoms.

The CDC recommended non-contact temperature assessments to be conducted at homeless shelters and encampments.1 Yet, the World Health Organization and the CDC acknowledge this may be inadequate since asymptomatic individuals might be able to spread the virus.2

Some companies in the U.S. instituted temperature checks for associates returning to work. Amazon announced they were doing this on more than 100,000 workers each day.3

Yet, in one study of 5,700 people triaged for hospitalization with COVID-19, researchers found only 30.7% had a fever.4 Infectious disease doctor from Johns Hopkins Center for Health Security, Dr. Amesh Adalja, spoke with a reporter from Health, saying:5

“Fever screening can be one part of a wider system, but it’s still unclear how much marginal benefit there is. Prevention of infection with the new coronavirus is a multi-faceted task. Even with entry screening in place, it’s very important to still wash your hands and practice good hand hygiene throughout the day. For those at high risk, it will also be important that they continue to optimally social distance even when venues are open.”

Data Show Smell and Taste Impairment Predicts COVID

There has not been a definitive study on the number of people with COVID-19 who also have a fever.6 New research published in JAMA offers a clue that fever may not be as common with the virus as originally believed.

Until more information is available, scientists are relying on data from the SARS epidemic in 2003 to assess COVID-19 patients. In one literature review published in 2009 following SARS, the researchers found that fever had a negative predictive value ranging from 86.1% to 99.7%.7

This means that those without a fever likely did not have SARS. However, the same cannot be said for COVID-19, as some people are contagious before they run a fever, and others may never get a fever. While temperature taking may only catch a small number of those with an infectious disease, some experts are suggesting that adding a smell test to screenings would be more effective.

It’s also important to remember that you can run a fever for reasons other than COVID-19. There is a growing body of evidence to suggest that people with the virus have a higher rate of smell and taste dysfunction, including complete loss, which is called anosmia (loss of sense of smell) and ageusia (taste). Andrew Badley is a leader of a virus lab at Mayo Clinic. He spoke with a Stat News reporter, saying:8

“My impression is that anosmia is an earlier symptom of Covid-19 relative to fever, and some infected people can have anosmia and nothing else. So it’s potentially a more sensitive screen for asymptomatic patients.”

What Are the Numbers?

Badley and his colleagues published a study in April in which they evaluated the clinical notes of 77,167 patients who had undergone PCR testing for COVID-19.9 They compared those results to the patients’ electronic health records and found that 2,317 were positive and 74,850 were negative.

The team then identified and analyzed symptoms associated with COVID-19, including fever and chills, respiratory difficulty, cough, muscle pain, diarrhea and smell dysfunction. Those who tested positive were 27.1 times more likely to have smell and taste dysfunction than those who were negative.

This was significantly higher than any other symptom analyzed. The closest was fever and chills, which presented a 2.6 times greater likelihood that the person would have the virus. In a separate study published in the International Forum of Allergy and Rhinology, researchers did a retrospective review of patients who came to the San Diego Hospital system between March 3, 2020 and April 8, 2020.10

They included those with a confirmed positive infection who also had an evaluation of smell and taste function. There were 128 who met the criteria. Of those, 20.1% required hospitalization. In further analysis, the team demonstrated:11 

“Admission for COVID19 was associated with intact sense of smell and taste, increased age, diabetes, and subjective and objective parameters associated with respiratory failure. On adjusted analysis, anosmia was strongly and independently associated with outpatient care …”

Data gathered from 220 survey respondents across the U.S. showed the symptom of loss of smell or taste was even higher.12 Of the respondents, 42% were COVID-19 positive and 58% were not. The loss or alteration in smell or taste as the first or sole symptom occurred in 37.7%.

Separately, a review of the literature was conducted to include 24 studies from 8,438 lab-confirmed positive COVID-19 patients across 13 countries.13 The researchers found smell dysfunction was found in 41% and taste dysfunction was present in 38.2% of the population.

Why Might Smell and Taste Be Affected?

Dr. Justin Turner from Vanderbilt University Medical Center believes the prevalence of anosmia in the population with COVID-19 is 25%, and it may be as high as 80%, based on patients’ subjective reports.14 He also hypothesized how it may happen. He believes the primary cause is an inflammatory reaction brought about by the virus inside the nasal cavity near the olfactory nerve. He explains:15

“In COVID-19, we believe smell loss is so prevalent because the receptors for COVID-19 that are expressed in human tissue are most commonly expressed in the nasal cavity and in the supporting cells of the olfactory tissue. These supporting cells surround the smell neurons and allow them to survive.”

Infection of the nasal epithelium also appears to be higher in adults. The authors of a study published in the Journal of the American Medical Association linked the low infection rate in children (less than 2%) with the hypothesis that they have a lower expression of ACE2 receptors than adults.

They found that age was a risk factor based on the number of ACE2 receptors in the nasal cavity, “the first point of contact for SARS CoV-2 and the human body.”16 Your sense of taste is dependent on smell, so it makes sense that when smell is altered you also have an alteration in taste.

I also wonder how much zinc deficiency or insufficiency may have to do with the loss of smell. Data gathered for a study published in the International Forum of Allergy and Rhinology showed that those who were admitted with more severe disease had an intact sense of taste and smell. One of the symptoms of zinc deficiency is a loss of sense of smell.17

We know the body uses zinc intracellularly to stop viral replication and slow or stop the infection.18 Could it be that individuals who get more zinc into the cells and use it to slow the infection also demonstrate symptoms of zinc insufficiency or deficiency as their body uses the trace element to fight the virus?

How to Test for Zinc Deficiency

Zinc is important to all organs and cell types, which explains the varied symptoms associated with deficiency. It is required for approximately 100 enzymes and is crucial for your immune function, wound healing, cell division and growth and development. Researchers believe that zinc deficiency:19

“… is strikingly common, affecting up to a quarter of the population in developing countries, but also affecting distinct populations in the developed world as a result of lifestyle, age, and disease-mediated factors.”

In North America, overt deficiency is uncommon and related to inadequate intake, increased losses or requirements. For instance, bioavailability is lower with a plant-based diet and some have found that vegetarians need 50% more of the recommended daily allowance than those who eat meat.

However, it is not uncommon to have a mild or moderate zinc insufficiency. Since the trace element is important in the fight against viruses, including SARS-CoV-2, you may want to consider taking a simple zinc test at home to determine your status.

In the video below Dr. Donald Ozello demonstrates a simple taste test that can quickly tell you how insufficient or deficient in zinc you might be. Simply place two tablespoons of a solution of zinc at room temperature in your mouth and hold it. The results are based on what you taste after 10 seconds.

  • Grade 1 — An immediate bad taste, meaning you have no deficiency
  • Grade 2 — A moderately bad taste, indicating you have a mild deficiency
  • Grade 3 — A slightly unpleasant taste or delayed taste, which means you are deficient
  • Grade 4 — No taste, which means you are severely deficient

Combine Quercetin and Zinc for a Powerful Immune Boost

For zinc to work it must first get into the cell. Your body uses zinc ionophores, or substances that open the cell membrane for it to pass through. Drugs like chloroquine and hydroxychloroquine are zinc ionophores, which likely explains how they affect those with COVID-19 when the drugs are combined with zinc.

The good news is there are other substances that have the same action without the side effects. In a lab study published in 2014, scientists evaluated quercetin and epigallocatechin gallate (EGCG found in green tea) for the biological activity that may increase cellular zinc uptake. They concluded:20

“The ionophore activity of dietary polyphenols may underlay the raising of labile zinc levels triggered in cells by polyphenols and thus many of their biological actions.”

Quercetin and EGCG also have the advantage of inhibiting an enzyme used by coronavirus to infect healthy cells.21 Adding to this, quercetin has potent antiviral activity in its own right.22 When considering supplementation, it’s important to remember that excessive zinc may increase health risks. Acute side effects include nausea, vomiting, diarrhea, abdominal cramps and headaches.23

Another important factor relating to immune health is the balance of copper and zinc; an increased intake of zinc may help. Chris Masterjohn writes this as little as 60 milligrams of zinc per day can introduce problems.24 Essentially, copper lowers the activity of superoxide dismutase, sometimes called SOD. This is a crucial to your immune defense. He recommends:

“Zinc that is swallowed for the sake of reaching the lungs should be used preventatively rather than at the first sign of symptoms, because it takes a long time to enrich systemic stores of zinc.

I prefer to use 1-3 zinc lozenges per day preventatively so that the tissues of the nose and throat are rich in zinc as soon as they encounter the virus. Unlike swallowed zinc, however, lozenges designed to spread zinc through these tissues can be jacked up quickly in response to symptoms, because their ability to spread zinc through these tissues is not limited by intestinal zinc transporters.”

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