The role of close contacts of COVID-19 patients in the SARS-CoV-2 transmission: an emphasis on the percentage of non-evaluated positivity in Mexico

Martinez-Fierro, Margarita L.; Ríos-Jasso, Jorge; Garza-Veloz, Idalia; Reyes-Veyna, Lucia; Cerda-Luna, Rosa Maria; Duque-Jara, Iliana; Galvan-Jimenez, Maribel; Ramirez-Hernandez, Leticia A; Morales-Esquivel, Andres; Ortiz-Castro, Yolanda; Gutierrez-Camacho, Jose R; Valdes-Aguayo, José J; Vargas-Rodriguez, Jose R

OBJECTIVES: To determine the percentage of positivity of close contacts of coronavirus disease 19 (COVID-19) patients to depict the importance of asymptomatic infections in the patient-to-patient transmission of COVID-19. METHODS: One hundred subjects were included. Nineteen index COVID-19 cases and eighty-one traced close contacts were screened for coronavirus 2 of severe acute respiratory syndrome (SARS-CoV-2) using real-time reverse transcription-polymerase chain reaction (RT-PCR). Immunoglobulin M (IgM) and G (IgG) against SARS-CoV-2 were evaluated by rapid test. RESULTS: Thirty-four (42%) contacts in the study were positive for SARS-CoV-2. Twenty-three (67.6%) manifested less than two respiratory symptoms, and five (14.7%) remained asymptomatic. The average of positive contacts by index COVID-19 case (R(0)) was 4.3 and the mean of time of positive COVID-19 test at sampling time was 18.9 days. Positive antibody test against SARS-CoV-2 was observed in 16% of the participants. CONCLUSION: The proportion of close contacts of COVID-19 patients infected with SARS-CoV-2 (42%) and with less than two or with no respiratory symptoms (82.4%) was high in the study population. A low proportion of COVID-19 patients had a positive test for antibodies against SARS-CoV-2. The screening for SARS-CoV-2 in close contacts of COVID-19 positive patients should be encouraged to avoid spreading the infection and the expansion of the disease.