History of the primary case:
January 17: A 21-year old student from Shenyang (Patient A) travelled to Wuhan with 5 classmates on January 17 and returned on January 20 by air while wearing masks. Her father picked her up at the airport at 3：30 pm via personal car, where both wore masks, to return home, and no one wore masks at home.
January 20 Evening: Patient A had dinner with her boyfriend, who later became Patient D, at 8 pm for 3 hours in a fast-food restaurant.
January 21: Patient A participated in a family dinner with seven other relatives including her father, mother, grandfather, grandmother, uncle, aunt, and cousin. All those at the dinner were later quarantined at home for 14 days. Besides her parents, the other five family members who attended the dinner showed no symptoms and their throat swabs tested negative for COVID-19 using RT-PCR.
January 22: Patient A had a party with 11 friends for 6 hours including her boyfriend. They were later quarantined at home for 14 days.
January 23: Patient A became symptomatic around 4 pm with no previous symptoms. She then began having nasal congestion, runny nose, fatigue, headache, and fever (37.3 ℃). Her fever increased to 38.7 ℃ that night. Her father (Patient B) also had a fever that started at 6 pm the same day.
January 24: Patient A and B went to the hospital together where both tested positive for COVID-19 by RT-PCR. They were diagnosed as confirmed cases and isolated at hospital.
January 25: The mother (Patient C) of Patient A was under self-isolation at home, experienced onset of fever, and was laboratory confirmed with COVID-19 on January 26.
January 27: Patient A’s boyfriend experienced onset of fever and was confirmed with COVID-19 on January 28. They only met twice at restaurant on 20 and 22, respectively. Among the four total cases in this cluster, only Patient A had traveled outside of Shenyang or had traveled to Wuhan, and none of the other three patients had traveled or had contact with another confirmed case (Table 1).
Case Sex Relationship to patient A Age Onset of symptoms Laboratory confirmation Date of diagnosis Travel history A Female Self 21 January 23 Confirmed January 24 Flight to Wuhan 1/17 Return 1/20 B Male Father 44 January 23 Confirmed January 24 No travel C Female Mother 45 January 25 Confirmed January 26 No travel D Male Boyfriend 21 January 27 Confirmed January 28 No travel
Table 1. The cluster of COVID-19 cases by age, sex, onset of symptoms, laboratory confirmation, and travel history in Shenyang, China, 2020.
Among the 11 friends who had the party with patient A, one friend, who sat next to patient A at the party, developed fever (37.9 ℃), sore throat and productive cough on Jan 25. However, her two successive throat swabs showed negative RT-PCR results for COVID-19. The other 10 friends showed no symptoms and their throat swabs all showed negative RT-PCR results for COVID-19 after 14 days quarantine.
Of the five other classmates that had traveled to Wuhan with Patient A, none developed symptoms during the 14 days of self-quarantine. Their throat swabs tested negative by RT-PCR for COVID-19. Everyone in the group who traveled to Wuhan bought duck snacks, a Hubei-Province delicacy, for their families and no further cases were found among those who ate the snacks. Figure 1 showed the epi curve of the 4 cases (Figure 1).
From the 4 cases, 43 contacts were identified, and all contacts were quarantined at home for 14 days and showed no symptoms. Patients were immediately isolated at the hospital when they were confirmed.
Among the 169 passengers and 14 crew who were on the flight returning from Wuhan to Shenyang with Patient A, another confirmed case of COVID-19 was found among the passengers. This passenger became febrile on January 25 and was COVID-19 confirmed on January 28 in Jiamusi, Heilongjiang Province. After arriving in Shenyang by air he traveled by train to Changchun on January 20. His 3 family members were infected in the several days following his return home. This passenger was seated 13 rows apart from Patient A, did not know Patient A. The passenger said that he did not show any symptoms on the plane.