Overall, considering the epidemiological follow-up of 154 asymptomatic individuals, 103 (66.9%) remained asymptomatic, and 51 (33.1%) developed symptoms. The patients who remained asymptomatic were 55 women and 53 men (n = 103), and their age distribution was as follows: 17 pediatric patients (0–17 years), 20 young people (18–26 years), 53 adults (27–59 years), and 18 elderly (> 60 years).
The 51 patients who developed symptoms of the disease (presymptomatic) were 22 women (43%) and 29 men (57%). No statistically significant differences were found when comparing men and women (p = 0.327). The most frequent clinical manifestations in men were dyspnea, cough, fever, epigastralgia, and headache, while in women, they were adynamia, anosmia, arthralgia, ageusia, odynophagia, diarrhea, myalgia, and chest pain (Fig. 1).
The average time of conversion from the asymptomatic to symptomatic status was between 1–3 days (43.1%), 4–7 days (19.6%), 8–10 days (3.9%), and between 11–15 days (9.9%); 23.5% did not remember the time concerning the onset of symptoms. The median Cq of asymptomatic patients was 37.35, and that of symptomatic patients was 35.24.
The main symptoms for all age groups were headache, fever, and anosmia (Table 1). When performing the principal component analysis for each of these groups, it was determined that in the elderly, the main manifestations were epigastric pain, dyspnea, and headache. In adults, the most common symptoms were cough, ageusia, and odynophagia, while in young people, they were anosmia and arthralgia (Fig. 2).
Table 1
Distribution of symptoms according the age.
Symptoms
|
Young1 %
|
Adult2 %
|
Elderly3 %
|
Total %
|
Headache
|
(4/10) 0,08
|
(10/28) 0,20
|
(7/13) 0,14
|
(21/51) 0,41
|
Fever
|
(2/10) 0,04
|
(10/28) 0,20
|
(8/13) 0,16
|
(20/51) 0,39
|
Anosmia
|
(3/10) 0,06
|
(8/28) 0,16
|
(2/13) 0,04
|
(13/51) 0,25
|
Cough
|
(2/10) 0,04
|
(10/28) 0,20
|
0
|
(12/51) 0,24
|
Adinamia
|
(1/10) 0,02
|
(9/28) 0,18
|
(1/13) 0,02
|
(11/51) 0,22
|
Dyspnoea
|
(2/10) 0,02
|
(4/28) 0,08
|
(5/13) 0,10
|
(10/51) 0,20
|
Diarhrea
|
(2/10) 0,04
|
(6/28) 0,12
|
(2/13) 0,04
|
(10/51) 0,20
|
Ageusia
|
(2/10) 0,04
|
(7/28) 0,14
|
(1/13) 0,02
|
(10/51) 0,20
|
Odynophagia
|
(2/10) 0,04
|
(7/28) 0,14
|
0
|
(9/51) 0,18
|
Myalgia
|
(1/10) 0,02
|
(5/28) 0,10
|
(2/13) 0,04
|
(8/51) 0,16
|
Arthralgia
|
(2/10) 0,04
|
(6/28) 0,12
|
0
|
(8/51) 0,16
|
Pain of thorax
|
0
|
(3/28) 0,06
|
(2/13) 0,04
|
(5/51) 0,10
|
Epigastralgia
|
0
|
0
|
(1/13) 0,02
|
(1/51) 0,02
|
Young1 18–26 (included one child of 12 years old); Adult2 27–59 years; Elderly3 > 60 years. |
Four elderly patients who became symptomatic died, three men with comorbidities (heart disease, cancer, and kidney disease) and one woman without comorbidities. This last patient passed away during medical care at her home. It is important to note that deceased individuals' Cq values (median 29.93) were lower than that of asymptomatic and symptomatic individuals (median 37.35 and 35.24, respectively).
This study is the first to be carried out in Colombia on the change in status from presymptomatic to symptomatic. In this study, it was found that 33.1% of the patients were in a presymptomatic state, and four (8%) of them died. This significant proportion could mean an eventual silent transmission, contributing to increased cases in the epidemic associated with SARS-CoV-2 (5).
There are models to estimate the transmission rate of asymptomatic infections from unknown sources, and they are estimated at 55%; in documented cases, it is estimated to be around 79% (6). Our study cannot infer these proportions; however, it highlights that 33.1% could have had an actual weight in the increase in cases at the time. Other reports had described that 31% (5/16) of the transmissions occurred before the symptoms appeared. In our case, this critical epidemiological data is unknown. However, in a study carried out in China with a smaller number of patients than our study, they found 19 asymptomatic cases and five presymptomatic cases and found that only 4.2% (1/24) of the cases resulted in secondary transmission (7). According to the authors (7), the low asymptomatic/presymptomatic transmission rate could have been due to people's isolation during the outbreak. A similar situation happened in Colombia, but our 33.1% proportion was higher than them. However, other studies (7) of indirect transmission have shown that symptomatic cases transmitted SARS-CoV-2 to 16.2% (34/210) of domestic contacts; but there was no asymptomatic or presymptomatic spread in 15 of the domestic contacts. Finding different from ours found 33.1%.
On the other hand, our findings demonstrated that the most common clinical manifestations in individuals who evolved to symptoms were headache, fever, and anosmia. These findings agree with Fu et al. (8), who found that the main clinical manifestations of COVID-19 are fever, headache, cough, and dyspnea.
According to age, it was observed that the most common symptoms were anosmia and arthralgia in young people. Young individuals do not seem to have significantly lower respiratory tract involvement. However, SARS-CoV-2 infection significantly affects the upper respiratory tract, mainly causing neurological manifestations such as olfactory dysfunction, lasting up to 28 days (9). Anosmia can be a pathognomonic clinical manifestation that could be used by healthcare personnel to differentiate SARS-CoV-2 infection from other respiratory viruses such as influenza (10). Another study in Korea also evidenced anosmia as a frequent symptom in 3,191 young people with COVID-19 and was characteristic in mild forms of the disease (11).
In adults, the most important clinical manifestations were cough, ageusia, and odynophagia, consistent with what was published (12). It is striking to show that another neurological manifestation such as ageusia is one of the most frequent clinical symptoms during SARS-CoV-2 infection, which could be associated with greater involvement of the virus on the glossopharyngeal, facial, and vagus nerves in this age group (13). Therefore, ageusia could serve as a pathognomonic symptom to make a diagnosis in the adult population.
In the elderly, the clinical manifestations were epigastric pain, dyspnea, and headache. Dyspnea was in the present work a specific manifestation of older adults infected by SARS-CoV2 (14). Dyspnea should be considered a clinical symptom with a poor prognosis, mainly in patients with comorbidities such as hypertension, cardiovascular disease, COPD, and kidney disease (15, 16).
Regarding the clinical manifestations related to gender, in this study, it was established that in men, a more significant compromise of the lower respiratory tract (cough, dyspnea) was significant would be related to greater severity and a worse clinical prognosis for COVID-19 (15). While in women, mild nonspecific clinical symptoms of the upper respiratory tract were found, which could be related to a less severe infection. These findings are in agreement with Jin et al. (17), who showed that the clinical manifestations in men were more severe than in women and a healthier lifestyle could explain this in women and by biological and immunological differences such as high expression of the ACE2 receptors for SARS-CoV-2 in men (18).
Of the 51 individuals who became symptomatic, 4 (8%) of them died. Advanced age could be related to mortality (mean 69, range 62–75). Besides, they had comorbidities such as cancer, heart disease, and kidney disease. It is also interesting to mention that they had high viral loads with Cqs between 17.95–36.62. In the future, asymptomatic patients with high viral loads should be closely monitored by healthcare personnel.
The present study has some limitations; first, we do not know how long asymptomatic individuals were infected while in contact with other individuals before diagnosis. The study also did not include data on the observed incubation period, and our data could be limited mainly to the Colombian Caribbean population.
In conclusion, the present study demonstrates the importance of performing diagnostic tests among the contacts of individuals positive for SARS-CoV-2 since they could behave as direct disseminators of the disease. The detection of asymptomatic and presymptomatic individuals allows epidemiological screening and control of the proliferation of cases. Because of the high proportion of presymptomatic patients found in the present study and without the guarantee of a vaccine for Latin America in the next seven months, we believe that in the absence of symptoms, we have as our only the following weapons: social distancing, the use of face masks, and adequate hands hygiene. The result indicates that the country's Public Health authorities must return to intensive tracking of apparently healthy contacts or people.