The common symptoms at onset of illness in the findings were cough, running nose, fever, headache and sore throat; while the less common symptoms were vomiting, diarrhea, nausea as well as abdominal pain and joint pain. The highest proportion of cases (37.5%) presented symptom in the 1st tertile denoting onset within three days after laboratory confirmation for SARS-CoV-2; while the rest had symptoms either in the 2nd (31.4%) or 3rd tertile (31.4%) denoting 4–6 days and at-least 7 days after exposure, respectively. Running nose and chest pain were less likely to occur in the 1st tertile (RRR = 0.45, 95% CI 0.24–0.84) and 2nd tertile (RRR = 0.64, 95% CI 0.09–0.72) rather than in the 3rd tertile. Cases aged 20–29, 30–39, 40–49 and above 49 were less likely to have symptoms in the 1st and 2nd tertile compared to those aged below 20 years (p < 0.05).
The clinical features of patients infected with the 2019 novel coronavirus in Uganda are to a greater extent similar with recent findings of patients diagnosed with the virus in Wuhan, China . The patients in Wuhan, China presented common symptoms at onset of illness to be fever, cough, and myalgia or fatigue while the less common symptoms were sputum production, headache, haemoptysis, and diarrhoea. Both studies present cough and fever as common symptoms at onset of illness and diarrhea as less common symptom. However, headache was established as one of the common symptoms at onset among patients in Uganda while it was established among the less common symptoms in Wuhan, China. Further, muscle and joint pain were established as less common symptoms at onset in Uganda while these were established among the common symptoms in Wuhan, China. This evidence shows both similarities and differences in epidemiological characterization of cases exposed to COVID-19 in Uganda and elsewhere.
Running nose and chest pain were less likely to occur in the 1st tertile and 2nd tertile rather than in the 3rd tertile. The chest pain is considered as one of the emergency warning signs and symptoms for COVID-19 including trouble breathing, persistent pain or pressure in the chest, confusion or inability to arouse the person, or bluish lips or face (12,13). It is highly unlikely that these signs or symptoms will present at the initial stages of the illness. Therefore, evidence of these implies that COVID-19 symptoms have worsened after several days of the illness; which is more likely in the latter stages of the incubation period. It’s an indication of disease progression from mild to severe form of COVID-19 illness.
It is evident in the findings that symptom onset in the 1st and 2nd tertile was less likely among cases aged at-least 20 years compared to the younger ones. In other words, the cases aged below 20 years were more likely to have symptom onset earlier after exposure to COVID-19 compared to their older counterparts. Though the younger age group onset of symptoms occurred earlier than the older age-groups, the symptoms were indications of mild disease rather than severe illness. Our findings seems to concur with evidence suggesting that older people (that is people over 60 years old) are at a higher risk of getting severe COVID-19 disease(13,14) In particular, the literature suggests that the risk of severe disease gradually increases with age starting from around 40 years. We cannot be able to substantiate the literature since the cases in our study are predominantly a young population (median age is 33 years, IQR = 26–41). The fact that symptom onset in the 1st and 2nd tertile was less likely among cases aged at-least 20 years, one would not expect onset and severe disease to occur at the same time in the 3rd tertile. Therefore, our findings present the young population (aged below 20 years) as a vulnerable group that needs to be given attention. More so, they can be a source of community spread of infection and a risk to the older generation.
Our study showed no significant variations in timing of onset for the following symptoms: fever, sore throat, shortness of breath, cough and headache (p > 0.05). Although marginally significant, it is worth noting that headache (p = 0.065) and chest pain (p = 0.052) were less likely to present in the 1st tertile rather than the 3rd tertile. Likewise, cough (p = 0.051) was less likely to present in the 2nd tertile rather than the 3rd tertile. Chest pain is considered as one of the emergency warning signs and symptoms for COVID-19, which is unlikely to present at the initial stages of the illness(13,14). On the other hand, we cannot substantiate the presentation of headache and cough in the 3rd tertile since these have not been identified among the emergency warning signs and symptoms for COVID-19 that would possibly present in the latter stages of the illness.
Studies have shown that majority of confirmed cases for the SARS-CoV-2 infection were males (14,19–21). Nevertheless, we found no significant variation in timing of symptom onset by sex (p > 0.05). This evidence seems contrary to studies in China, South Korea, United States, and Italy that have reported an association between the sex of COVID-19 patients and fatality rates as well as critically-ill status(13–16,19–21). For example, cases with fatality rates were higher in male patients than females (13–15), less female patients needed intensive care or died compared to male patients ; women were significantly less prone to develop the severe form of the disease (19); some symptoms were experienced significantly more by male than female, including cough and fever(20). In a study of sex differentials in COVID-19 patients, Maleki et al.(21) arguments for these variations include the following: women’s immune cells activate more than men, women produce lower levels of interleukin-6 (IL-6) compared to men, which is associated with better longevity; different levels of Angiotensin Converting Enzyme-2 (ACE2) in men and women, the effects of testosterone on ACE2 levels, and the fact that the ACE2 gene is located on the X-chromosome. In citing Fagone et al. (22), Maleki et al. (21) writes: “in age group of 40 to 60 years, the transcriptomic characteristics of female lung tissue has more similarities to COVID-19-induced characteristics compared to male tissue. A possible explanation of the lower incidence of COVID-19 in female patients could be the lower threshold of acute immune response to COVID-19 in men when compared to women”.