The Covid Conundrum: Symptomatology and Determinants of an Outbreak

To assess the incidence of Anosmia and Dysgeusia in Covid-19 patients. The study also assesses the rate of asymptomatic transmission of Covid-19 in community outbreaks and the factors that leads to a higher prevalence in the immigrant population
Nikhil Srivalsan
Grade 10



  • If symptoms of Covid-19 are analyzed, then ANOSMIA and DYSGEUSIA are specific symptoms among those tested positive for Covid-19 and can help in the early detection of infection.


  • If there is a community outbreak of Covid-19,

-  Then immigrants (mostly first generation) are more at risk of acquiring  Covid-19 because of socio-economic factors.

-  Then the rate of asymptomatic infection will be close to 40%, because some individuals with a robust immune system may not exhibit symptoms. 


Testable Questions:

In a community cohort,

  • What is the incidence of Anosmia and Dysgeusia and how do females exhibit OTD (Olfactory and Taste Dysfunction) symptoms compared to males?

  • Were there any immigrant communities at higher risk of Covid-19 exposure and infection?

  • What is the rate of asymptomatic infection? Which age group is likely to have a more asymptomatic infection?



Youtube Link to Presentation:


Research Method: 

  • This is a retrospective cohort study.

  • All patients in the community clinic who were tested positive for Covid-19 from 1st March 2020 to 31st Dec 2020 were included in the study.

  • Study based on data and inputs collected (through physicians who were providing care at a community clinic - Calgary SW) to my questionnaire.

  • The study was done in collaboration with community physicians who were involved in the care of patients affected by Covid-19. The patient data was kept confidential by the physician and only relevant inputs required for my study were provided. 

  • The data compiled to my questions were analyzed and results reviewed. My hypothesis was tested with the results obtained to derive conclusions.



Study Questionnaire:

  • Total Number of Covid-19 positive patients from 1st March 2020 to 31st Dec 2020

  • Male/Female Ratio: -  Distribution of Covid-19 tested positive patients

  • Age Distribution

 a) Under the age of 1-year b) 1-5 years  c) 6-12 years

 d) 13-19 years e) 20-40 years  f) 41-60 years  g)  61-70  years  h) Greater than 70 years


  • Distribution of Covid-19 tested positive patients (Geographic Region of Origin-Patients) 

a) North America (USA/Canada) b) Central America c) South America

 d) East Asia e) South Asia f) South East Asia g) Central Asia h)  North Asia

 i) Middle East  j) North Africa k) East Africa l) West Africa

 m) Southern Africa (South Africa/Zimbabwe etc)

  n) Eastern Europe  o) Western Europe   p) Oceania (Australia/New Zealand/Hawaii)


  • Duration of Covid-19 Symptoms

      a) Less than one-week b) 1 – 2 weeks   c) 2- 4 weeks

      d) More than one-month e) Asymptomatic


  • Status of Covid-19 positive patients

     a) Isolated at Home  b) Hospital Admission c) ICU Admission  d) Death


  • What are the most common symptoms noticed within 72 hours before or after Covid-19 testing?

      a) Cough  b) Fever   c) Rhinorrrhea  d) Anosmia e) Hyposmia        f) Dysgeusia

      g) Ageusia h) Hypogeusia  i) Asthenia  j) Myalgia  k)           Headaches  l) Loss of Appetite

      m) Gastro-Intestinal (GI)  Symptoms  n) Sore Throat  o)   Dyspnoea -Shortness of Breath

      p) Asymptomatic  


  • Risk Factors:

      a) Diabetes   b) Cancer   c) Asthma/COPD  d) BMI:30-35 (Low Risk Obese);   BMI:35-39.9 (Moderate Risk Obese);  BMI:>40 (High Risk Obese)    

       e) BMI: 25 TO 29.9 (Overweight)  f) Smoker

       g) Congestive Heart Failure (CHF)  h) Chronic Kidney Disease (CKD)

       i) Pregnancy  j) Age > 65 years     


  • Covid Swab Test Positive (Month Wise Numbers):   March 2020 to Dec 2020

  • Sources of Infection:

      a) Cargill Meat Plant (April 2020)  b) Lilydale Poultry Plant, Calgary (Aug 2020)

      c) Religious Gathering  d) School  e) Birthday Party f) Frontline Healthcare Workers

      g) Sick Contacts   h) Daycare   i) Travel  j) Restaurant  k) Unknown (Community spread)







Why this study?

  • A pandemic was declared on 11th March 2020  by WHO.

  • The world changed overnight. The novel coronavirus (SARS-CoV-2) has taken over our lives.

  • Covid-19 was initially screened for common symptoms like fever, cough, and shortness of breath symptoms. Subsequently, Anosmia (Loss of smell)  and Dysgeusia (Altered taste) have been added to CDC screening guidelines.

  • I wanted to assess the prevalence of Anosmia and Dysgeusia in Covid-19 patients as new research indicates that it is a very specific symptom for Covid-19 screening

  • We have not learnt lessons from SARS and H1N1. Lack of public health strategy affected the spread of disease.

  •  Cargill Meat Plant (near High River) - Largest outbreak in Canada resulting in over 500 cases and 3 deaths. How to prevent?



Covid-19: Olfactory and Taste Dysfunction Symptoms



Background Research:


  • Globally as of 1st March 2021, over 113 million people have acquired the infection and more than 2.5 million people have lost lives so far. 

  • The spread of the virus is incompletely understood.  The infectivity is very high.

  • Transmission through airborne route is controversial but has been proposed as well.

  • The incubation period is anywhere from 2-14 days.

  • At initial stages of pandemic, most common symptoms cough(50%), fever(43%), ,Myalgia(36%), headache(34%), dyspnoea(29%), sore throat(24%), diarrhoea(19%), Nausea and vomiting(12%), and low rate of  Anosmia and Dysgeusia  (10%)

  • Recent studies reported that Anosmia and Dysgeusia are among the earliest symptoms observed in Covid-19 patients.

  • Asymptomatic COVID 19 transmission is a major concern that is a deterrent in curtailing the spread of the virus. 

  • In several studies, the rate of asymptomatic infections has been described anywhere from 25 to 50 %. CDCs current best estimate states 40% asymptomatic cases. 




  • NAAT- Nucleic Acid Amplification testing from nasal, oral or nasopharyngeal swabs

  • RT-PCR (Reverse Transcriptase- Polymerase chain reaction) from nasal, oral  or nasopharyngeal swabs

  • Antigen testing – Not much done due to the high number of false-negative cases

  • Viral cultures, Chest X-rays and CT scans in hospitalized patients

  • Serology (Antibody) testing- Done to detect previous COVID 19 infection



Statistics & Awareness: 


Covid Clock:

As of 1st March 2021 (WHO Data)


Confirmed Cases: 113,820,000                                     

Deaths: 2,527,900


Confirmed Cases: 870,000

Deaths: 21,960

USA  (Highest Casualties)

Confirmed Cases: 28,345,500

Deaths: 510,910





  •   Please refer to the attached graphs summarizing my findings

    • Main Findings: First 5 graphs  (Graphs No. 2 to  5 cover the main points noted in the hypothesis) 

    • Additional Findings from study: Graphs No. 6 to 10  






1.OBSERVATIONS -  Anosmia & Dysgeusia:


  • The symptoms of  Anosmia and Dysgeusia are quite prominent in patients with Covid-19.

  • The cough was the predominant symptom( 49%), followed by Anosmia and Dysgeusia (40.6%),  fever (18%), rhinorrhea ( 16%), Myalgia/headache (14.8%). The least common symptoms were diarrhoea and dyspnoea.

  • Female patients are more likely to exhibit OTD symptoms. In my study,  the ratio was 2:1. 

  • Children were the least affected by the infection. Based on the research, this could be due to lower density of ACE2 receptors in the nasal mucosa.



2. OBSERVATIONS - Immigrants:


  • 95% of the patient infected belong to first-generation immigrants.

  • South east Asian first-generation immigrants (75%) were the ones affected predominantly. 

  • This is due to the fact that a lot of individuals from this community are employed in service sectors like meat plants, hospitals, long-term care, restaurants, and schools where the exposure is the highest.

  • They also have large families living under a single roof due to low income. Members of different families also carpool on a regular basis. This likely was key in the Cargill outbreak where many people got infected.


3. OBSERVATIONS - Asymtomatic Infection:

  • The rate of asymptomatic infection in my study was 20%, which is much lower than other studies and CDC's current best estimate of 40%.

  • The lower number in my study is likely due to reduced screening of asymptomatic individuals.

  • 20 % were totally asymptomatic and got tested only because their family members had tested positive.

  • We need rapid POC tests for faster screening of both symptomatic and asymptomatic patients.



  • In my cohort, the highest number of infections were from the ‘Outbreak at the Cargill Meat Plant’ at High River in April 2020. Multiple family members of the employees working at the meat plant also got infected.

  • It is observed that some of them work at multiple jobs to support the family, leading to the spread of Covid-19.

  • Maximum number of cases were in April 2020as a result of the ‘Cargill’ Meat Plant Outbreak. 61% of the patients became positive in April. The second highest is in November, about 10% where there was a resurgence in COVID cases.

  • In risk factors 10% of people had diabetes, 7% had a smoking history, 3% had asthma/COPD. 4.5% were Seniors. The majority of the patients did not have any risk factors to attribute to the infection.

  • Only a few seniors were affected by the infection (4.5%). It is because of the demographics in the clinic.

  • The age group that had the highest number of infections was between 20-60 (people with the highest productivity in the labor force)

  • Since early studies focused on hospitalized patients, the atypical symptoms in the outpatient population who are generally healthy may have been easily overlooked due to initial stringent testing guidelines in the early days of the pandemic.

  • 50% of patients recovered within 2 weeks and 21% of patients recovered within 4 weeks. Most of the patients only had mild symptoms.

  • There were only 2 patients who needed hospital admission. One of them was treated in the  ICU and was on a ventilator briefly. The majority recovered at home in isolation.






  • There is a strong association between Anosmia and Dysgeusia symptoms and SARS –Cov 2 positivity in line with my hypothesis. This distinctive symptom when present should help guide screening and testing for the virus.

  • The second part of my hypothesis is true. In my study, 96% of patients who acquired Covid-19 infections were immigrants (mostly first gen). Immigrants work in labor-intensive jobs and service sectors where there is overcrowding and reduced adherence to health guidelines. Further, socio-economic factors like low income and lack of education played a key role in the spread

  • The number of asymptomatic patients was about 20%. This is much lower than other studies and the CDC’s best estimate of 40% and deviates from my hypothesis.  This gap in number could also mean that we have to modify our screening protocols to catch these potential asymptomatic spreaders. 

  • The symptomatology profile continues to be updated with the increase of the prevalence of the virus.  

  • It is time for Canada to have its own solutions for pandemic preparedness and not rely on the international community. And we need to support and respect public health policies.




  • This study helps in gaining a renewed respect for public health.

  • Analysis of specific symptoms like Anosmia and Dysgeusia is very important for early detection of Covid-19.

  • The information gained from this study would help me better understand this complex viral illness and its implications.

  • This study would hopefully stimulate more research into how some of the identified socio-economic factors can be addressed by public health agencies to mitigate them in the future.

  • Since immigrants have been predominantly affected based on my study, hopefully, public health policies and measures can be taken to improve their working conditions.

  • Understanding asymptomatic transmission is very important in preventing the spread of Covid-19.



EXTENSION  (What Next....?)

  • Include a higher number of the patient population to get a larger sample by extending the study to get data from other community clinics (with different demographics) located in the city.

  • Assess the symptom of Anosmia and Dysgeusia using a control population with negative Covid-19 tests, but had a flu-like illness.

  • I want to shadow a specialist in infectious diseases and medical microbiology who is creating novel tools that enable us to develop a test that is portable and taken to the bedside where patients are quarantined (thereby preventing further transmission of viruses in public places).




  • “Coronavirus Disease (Covid-19): Symptoms and treatment”;  4Oct2020

  • “CDC - Symptom of coronavirus”;  4Oct2020

  • “ OECD - What is the impact of covid-19 pandemic on immigrants and their children”; 5Oct2020

  • “Statista - Number of novel coronavirus deaths by country”;  6Oct2020

  • “UpToDate - Clinical features of Covid19”; coronavirus-disease-2019-covid-19-clinical-features?  8Oct2020

  • “WHO - Coronavirus Disease(Covid-19) : How is it transmitted?”; 11Oct2020

  • “The Centre for Evidence-Based Medicine - Covid-19: What proportion are asymptomatic”; 14Oct2020

  • "PNAS - The implications of silent transmission for the control of COVID-19 outbreaks”; 14Oct2020

  • “AHS - COVID-19 Scientific Advisory Group Rapid Response Report” ; 18Oct2020

  • “Anosmia and Dysgeusia associated with Sars-Cov-2 infection “; . 20Oct2020

  • “Anosmia and Dysgeusia in Sars-Cov-2 infection: incidence and effects”; . 20Oct2020

  • “Military Medicine – Case Report : Covid-19 patient with chief complaint of Anosmia and Ageusia”; . 20Oct2020

  • “Can symptoms of Anosmia and Dysgeusia be diagnostic for Covid-19”; 20Oct2020

  • “CDC – Covid-19;Clinical Care Guidance”; 20Oct2020

  • “IDSA- Self-reported Olfactory and Taste Disorders in Patients with Sars-Cov2 infection”; . 20Oct2020

  • “CDC – Pandemic Planning Scenarios”; 20Oct2020

  • “Image – Action on Covid-19-CIFAR”; . 28 Feb 20





  • My teacher  Ms. Gierus for accepting my topic and providing the necessary support.

  • Dr. R. Natha and other physicians at the community clinic who have helped me with data for my study.

  • For all the authors who shared good research information on the internet

  • For school and Calgary Youth Science Fair Committee in giving me this opportunity to present my study.