Epidemiological study and health management of an imported incident of COVID-19 asymptomatic cases in Haikou, China: a retrospective case series

Background: To control the imported risks brought by all international arrivals, China Customs has implemented strict closed-loop health management policy called "three checks, three screenings and one transfer". This study provides epidemiological evidence for prevention and control measures on imported cases of asymptomatic infections and describes the current COVID-19 prevention and control system on imported risks in China. Methods: We retrospectively analyzed an imported incident of three asymptomatic carriers. Serum SARS-CoV-2 IgM and IgG antibodies were detected by chemiluminescence and gold immnnochromatography(GICA). Results: Three cases were reported positive for SARS-CoV-2 nucleic acid on their arrival, total antibodies and IgG, but negative for IgM. The Ct values of cases A, B and C were 34/36/36, 32/33/32 and 25/31/29, respectively. There were 10726434 pair-end reads sequenced for case C, and approximate 80% reads were aligned to the hCoV-19/Wuhan/IVDC-HB-01/2019 genome (EPI_ISL_402119). The viruses of case A and C were homologous and came from the SARS-CoV-2 variant. Conclusion: Serum antibody IgM and IgG tests are recommended for international travelers from epidemic areas. The "three checks, three screenings and one transfer" policy implemented at custom's entry points was effective in COVID-19 prevention and control.

Clinical and epidemiological investigation of a child with asymptomatic COVID-19 infection following reoccurrence.

Objective: To investigate the case of a child infected with coronavirus disease 2019 (COVID-19) who had subsequent viral reactivation. Methods: We retrospectively analyzed the clinical manifestations, epidemiological data, laboratory and imaging examinations, treatment, and follow-up of the child. And then, we searched related literature using PubMed. Results: The 9-year-old boy was exposed to COVID-19 in Malawi and tested positive for NAT in Haikou, China. He was asymptomatic and admitted to our hospital. After six negative NATs, he was discharged from the hospital and quarantined in a hotel. His infection was reactivated again after 22 days (interval between first and last positive NATs). The cycle threshold (Ct) values of positive tests were 25 and 31, and the gene sequencing viral loads were very low. The viral strain Kenya/P2601/2020, a variant of the hCoV-19/Wuhan/IVDC-HB-01/2019 genome (GISAID accession IL: EPI_ISL_402119), was found when polymerase chain reaction enrichment was used to sequence the virus. However, people around him tested negative for COVID-19. Conclusion: First, we confirmed the reactivation of COVID-19 in a child. The risk of recurrent infection with SARS-CoV-2 was low, and the policy of strictly isolating patients carrying long-term viral ribonucleic acid should be reconsidered. The interval positivity was most likely due to incorrect sampling and/or testing methods. SGS and aB testing are recommended for children with viral reactivation. Second, SARS-CoV-2 viral reactivation cannot be ruled out. The possible mechanisms, such as prolonged infection and viral latent reactivation, need further investigation.

Strategy on coping with COVID-19 vaccine hesitancy

Vaccine hesitancy is the major barrier for achieving protection for individual and population, reversing the progress achieved by immunization programs. Vaccine hesitance causes severe outcomes, and is the phenomenon emerges with the process of vaccination. Vaccine hesitancy lead to the diseases those have already been eliminated or well under controlled comeback or escalate into outbreak. Since the vaccine hesitancy impact continues to increase in recent years, vaccine hesitancy has been ranked one of the top ten global threats to human health. And now vaccine hesitancy is also the key barrier during the COVID-19 pandemic in controlling the disease globally and domestically by massively vaccinating. During the COVID-19 pandemic, the growing hesitancy is real, and reminds us that it cannot work if people refuse to be vaccinated, the herd immunity cannot be achieved, and there is limited chance to control the domestic sporadic epidemic and international imported risks. Vaccine hesitancy has complicated reasons, majorly categorized into vaccine confidence, including evaluation on safety and efficacy;complacency, including the underestimated disease burden and overconfidence on controlling the highly contagious disease;and convenience, including vaccine experimenting, producing, vaccinating and price. This article thoroughly analyses the background, causes, outcomes, hesitancy during COVID-19, and solutions to address vaccine hesitancy, to better increase the vaccine confidence among health care providers and the general public.

Epidemiological investigation of a COVID-19 family cluster outbreak transmitted by a 3-month-old infant.

OBJECTIVE: To investigate the clinical characteristics, epidemiological characteristics, and transmissibility of coronavirus disease 2019 (COVID-19) in a family cluster outbreak transmitted by a 3-month-old confirmed positive infant. METHODS: Field-based epidemiological methods were used to investigate cases and their close contacts. Real-time fluorescent reverse transcription polymerase chain reaction (RT-PCR) was used to detect Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) for all collected specimens. Serum SARS-CoV-2 IgM and IgG antibodies were detected by Chemiluminescence and Gold immnnochromatography (GICA). RESULTS: The outbreak was a family cluster with an attack rate of 80% (4/5). The first case in this family was a 3-month-old infant. The transmission chain was confirmed from infant to adults (her father, mother and grandmother). Fecal tests for SARS-CoV-2 RNA remained positive for 37 days after the infant was discharged. The infant's grandmother was confirmed to be positive 2 days after the infant was discharged from hospital. Patients A (3-month-old female), B (patient A's father), C (patient A's grandmother), and D (patient A's mother) had positive serum IgG and negative IgM, but patients A's grandfather serum IgG and IgM were negative. CONCLUSION: SARS-CoV-2 has strong transmissibility within family settings and presence of viral RNA in stool raises concern for possible fecal-oral transmission. Hospital follow-up and close contact tracing are necessary for those diagnosed with COVID-19.

Epidemiological characteristics of COVID-19 in Hainan Province, China

The epidemiology characteristics of 2019 novel coronavirus diseases (COVID-19) cases in Hainan were collected and analyzed for providing next stage control and prevention strategy in next stage. Spatial and temporal distribution, population characteristic, cluster, the interval between onset, visiting clinic, admitted were analyzed. Local cases and severe cases were also included in the analysis. Result showed that a total of 168 confirmed cases, including 36 severe cases and 5 fatal cases were reported. Cases were mainly distributed in Haikou, Sanya etc tourism cities and counties. The first case occurred in Jan 13th and the epidemic peak occurred in Jan 24th. Since Feb 6th, onset of illness has declined. The male-to-female ratio was 0.9:1. The median age was 51 years. Cases older than 50 years accounted for 54.8%. Retirees accounted for 36.9%, which was highest in all cases. Since Feb, the proportion of local cases rose dramatically. The period from onset to visiting clinic (OTV), from first visiting clinic to diagnosis (VTF), from onset to diagnosis (OTD) and from onset to be admitted (OTA) was longer in local cases than imported cases. Median age and the percentage of underlying diseases of severe/extreme cases were higher than mild/ordinary cases. OTV of severe/extreme cases was longer than mild/ordinary cases, while for VTF, the former was shorter than latter. The epidemic was divided into three stages. Most of cases in the first stage were imported cases, while in the second stage most of cases were local cases. There were few cases in the third stages. We should strengthen personal protection and health monitoring for people in service industry, isolate the close contacts, and carry out publicity and education to raise the awareness of medical treatment for people, especially for old people. Clinical doctors should monitor the state of the patients older than 60 years and with underlying diseases. We should step up epidemic monitoring prevention and control measure for people return from holiday and immigrant to consolidate the effects of prevention and control work.