INTRODUCTION The percentage of asymptomatic COVID-19 cases worldwide is estimated at 18–50%; 53% in Cuba specifically, and 58% in Havana, the Cuban capital and the 2020 epicenter of the country’s COVID-19 epidemic. These figures, however, do not represent the transmission capacity or behavior of asymptomatic cases. Understanding asymptomatic transmission’s contribution to SARS-CoV-2 spread is of great importance to disease control and prevention.
OBJECTIVE Identify the epidemiological implications of asymptomatic SARS-CoV-2 infection in Havana, Cuba, during the first wave of the epidemic in 2020.
METHODS We carried out a cross-sectional study of all confirmed COVID-19 cases diagnosed in Havana, Cuba, from March 16 through June 30, 2020. The information was obtained through review of the standardized form for investigation of suspected and confirmed cases. Examined variables included age, sex, occupation, case type and source of infection. Cases were divided into asymptomatic and symptomatic groups, and transmission was characterized through the creation of a contact matrix. Analysis was carried out in Epidat and R.
RESULTS We studied 1287 confirmed cases, of which 57.7% (743) were asymptomatic, and 42.3% (544) were symptomatic. Symptomatic presentation was the most common for both imported and introduced cases, while asymptomatic presentation was more common in autochthonic cases and infections from an undetermined source. Asymptomatic infection was more common in groups aged <20 and 20–59 years, while symptomatic infection was more common in those aged >60 years. In the contact matrix, 34.6% of cases (445/1287) were not tied to other cases, and 65.4% (842/1287) were infectious–infected dyads, with symptomatic–symptomatic being the most common combination. The majority of primary cases (78.5%; 1002/1276) did not generate secondary cases, and 85.6% (658/743) of asymptomatic cases did not lead to other cases (although one asymptomatic superspreader led to 90 cases in a single event). However, 63.2% (344/544) of symptomatic primary cases generated secondary cases, and 11 symptomatic superspreaders spawned 100 secondary cases in different events.
CONCLUSIONS Asymptomatic SARS-CoV-2 infection was the most common form of COVID-19 in Havana during the study period, but its capacity for contagion was lower than that of symptomatic individuals. Superspreader events under specific conditions played an important role in sustaining the epidemic.
KEYWORDS COVID-19, SARS-CoV-2, pandemics, asymptomatic infection, Cuba
INTRODUCTION COVID-19 is caused by the novel coronavirus SARS-CoV-2 and was declared a pandemic on March 11, 2020, the same day that the first cases in Cuba were diagnosed. In Cuba, all confirmed cases of COVID-19 were hospitalized from this point forward.
OBJECTIVE Characterize the first patients diagnosed with COVID-19 in Cuba.
METHODS We carried out a descriptive, cross-sectional study of 415 suspected cases of COVID-19 admitted to the Pedro Kourí Tropical Medicine Institute in Havana, Cuba, from March 11, 2020 through April 10, 2020. (In Cuba, all patients suspected of being COVID-19–positive were admitted to hospitals or isolation centers for observation and treatment.) Of these 415 individuals, 63 (15.2%) tested positive for SARS-CoV-2. Information was obtained from the Institute’s databases as well as a standardized interview form for cases confirmed or suspected as infected with the novel coronavirus. We considered the following variables: age, sex, occupation at the time of interview, national origin, personal health history, time elapsed between symptom onset and hospital admission, signs and symptoms, diagnosis and status at discharge. We based our analysis on frequency distributions and double-entry contingency tables.
RESULTS The mean age was 50 years (range: 16–94 years). The 45–54 age group represented the largest share of cases (25.4%; 16/63); persons aged ≥65 years were 20.6% (13/63); there were more men than women (55.6% vs. 44.4%). Cubans represented 52.4% (33/63) of patients while 47.6% (30/63) were from 14 countries where COVID-19 had already been identified. All foreigners and Cubans who arrived from abroad were considered imported cases (54.0%; 34/63). Health personnel (10 doctors and 1 nurse) represented 17.5% (11/63) of cases. Cough (50.8%), fever (46.0%), sore throat (22.2%) and headache (19.0%) were the most frequently reported symptoms. Asymptomatic patients represented 25.4% (16/63) of cases. Hypertension was the most frequently associated chronic disease (28.6%), followed by asthma (25.0%) and diabetes (17.9%). Patients who were admitted to hospital ≥3 days after symptom onset represented 66.7% (42/63) of cases. Mean hospital stay was 13.7 days (range: 1–27 days). Factors associated with a higher risk of contracting the disease included occupation as a healthcare worker (OR: 1.85; 95%, CI: 0.88–3.87) and aged ≥65 years (OR: 1.68; 95% CI: 0.85–3.34). Five individuals died, for a fatality rate of 7.9% (three foreigners and two Cubans; four men and one woman). Four of these patients were infected outside of Cuba and one was identified as a contact of a confirmed case. All patients who died had significant comorbidities (diabetes, asthma and hypertension). Age of deceased patients ranged from 54 to 87 years.
CONCLUSION The first patients diagnosed with COVID-19 in Cuba were admitted to the Pedro Kourí Tropical Medicine Institute in Havana. They share characteristics with those reported by other countries: more men than women were affected, and comorbidities including hypertension, diabetes and asthma were all important risk factors, as was age ≥65 years. More than half of all cases were imported, and autochthonous patients were all contacts of confirmed cases.
KEYWORDS Pandemics, COVID-19, SARS-CoV-2, Cuba
