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Containment of a Large SARS-CoV-2 Outbreak Among Healthcare Workers in a Pediatric Intensive Care Unit

Knoll, Rebecca Luise MD*; Klopp, Jonas MSc*; Bonewitz, Gloria*; Gröndahl, Britta PhD*; Hilbert, Katja*; Kohnen, Wolfgang PhD; Weise, Kerstin PhD; Plachter, Bodo PhD; Hitzler, Walter MD§; Kowalzik, Frank MD*; Runkel, Stefan PhD§; Zepp, Fred MD*; Winter, Julia MD*; Cacicedo, Maximiliano Luis PhD*; Gehring, Stephan MD*

Author Information
The Pediatric Infectious Disease Journal: November 2020 - Volume 39 - Issue 11 - p e336-e339
doi: 10.1097/INF.0000000000002866
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In Germany, SARS-CoV-2 infection in healthcare workers (HCWs) lead to temporary shutdown of at least 4 entire hospitals at the beginning of April. HCWs were put into quarantine, even with negative test results.1

SARS-CoV-2 infections in HCWs have the potential to reduce the number of available personnel but also to introduce the virus into the hospitals aggravating the already challenging situation.2 Notably, in the midst of the current pandemic, many countries worldwide are facing a shortage of HCWs while the number of patients continues to increase.

Many guidelines from healthcare authorities around the world have strongly supported the implementation of measures decreasing intrahospital outbreaks, thereby guaranteeing continuity of medical care.3 We would like to complement these directives by sharing our experience regarding the strategy we used to detect an outbreak in HCWs, and the measures implemented to efficiently contain it while avoiding the shutdown of the PICU.



The present study reports the outbreak of SARS-CoV-2 among HCWs of a pediatric intensive care unit (PICU). Clinical symptoms, their duration, RT-PCR-findings and virus persistence among the infected individuals were recorded. Furthermore, the effectiveness of containment measures was assessed.

Participants and Setting

The children’s hospital of the University medical center Mainz is located in the southwestern part of Germany and employs a total of 432 HCWs. Within the children’s hospital, the PICU is in charge of 10 beds for critically ill children cared for by 56 HCWs (44 nurses and 12 medical doctors). It is the only PICU in this district and therefore represents a critical part of the regional healthcare system for children and adolescents.


Interpersonnel contacts were traced from March 1, and screening of contact and/or symptomatic individuals throughout the children’s hospital were implemented.

Contact was defined as >15 minutes of direct and unprotected face-to-face contact. Symptoms from HCWs that made them eligible for screening included fever, cough, shortness of breath, rhinitis, headache, sore throat, diarrhea and general malaise within the last 14 days. Contact screening was performed by 3 consecutive tests, every 2–3 days. Symptomatic HCW was screened on the day of onset of symptoms. One month after the first positive test, we repeated a mass screening of almost all HCWs of the children’s hospital.

With the identification of the first positive HCW in the PICU, additional hygiene measures were implemented (continuous wearing of surgical masks by the entire staff, physical distancing and reinforcing hand hygiene). In line with the German governmental advice to reduce social contact in private to a minimum, all contact persons were encouraged to adhere to these guidelines. Under these measures, symptomatic HCW was allowed to continue working if they felt capable and test results came back negative.

SARS-CoV-2 infected people went to home-quarantine for at least 14 days. Thereafter, testing for SARS-CoV-2 was repeated, return to work was allowed after 2 negative test results within 24 hours.


Several real-time PCR-based testing systems from self-collected nasopharyngeal swabs were used to test for viral RNA of SARS-CoV-2. The swabs were collectively taken from the tonsils, pharynx and nose.

The first sample was tested with the QIAstat-Dx Respiratory 2019-nCoV Panel (QIAGEN, Hilden, Germany). Further tests followed using the RealStar SARS-CoV-2 RT-PCR kit by altona diagnostics (altona Diagnostics, Hamburg, Germany) and the cobas SARS-CoV-2 test (Roche, Mannheim, Germany).

Statistical Methods

Because of the descriptive nature of the report, statistical analysis for significance was not performed. Medians and ranges were used to describe continuous variables, counts and percentages to display categorical variables. All graphs and statistical calculations were created and performed using the python programming language version 3.7.3 with the matplotlib.pyplot library and Pixelmator Pro Version 1.6.1.


On March 13, 1 HCW of the PICU (ID 44) was identified with COVID-19 symptoms and immediately (within 1 hour) diagnosed via a PCR-based point-of-care testing method (QIAstat-Dx Respiratory 2019-nCoV panel), available on the PICU. Instantly, after the positive test result was known, strict containment measures and extended screening of the personnel were implemented throughout the children’s hospital, see above (Fig. 1).

A symptomatic HCW introduced SARS-CoV-2 to the PICU. Another HCW on the PICU was tested positive. Wearing of surgical face masks, reinforced hand hygiene, physical distancing, contact tracing and systematic screening and an emphasis on physical distancing were implemented immediately. Positively tested HCWs were sent into quarantine. Mass screening took place 1 month later.

Screening and Virus Transmission

In total, we performed 578 RT-PCR-based screenings throughout the children’s hospital. From a total of 432 HCWs, 91 (21%) were eligible for screening after the first positive test result on the PICU due to direct contact and/or symptoms. From the 14–27 of April (1 month after the first positive case), additional mass screening (independent of contact or symptoms) of 316 HCWs was performed throughout the children’s hospital. After the identification of the first positive case via the point-of care testing on the PICU on March 13, we identified a total of 7 SARS-CoV-2 positive staff members by March 18. On March 23, an eighth staff member was identified being positive on the third nasopharyngeal swab. All infected HCWs were working at the PICU and had direct “unprotected” contact with each other before March 13 (Fig. 2). HCW 35 was probably the index patient, initially on sick leave, then working with moderate symptoms on March 1 and was again on sick leave afterward. After implementation of containment measures, virus transmission stopped and no staff member outside the PICU was diagnosed positive.

A network plot of the connections (edges) that each positively tested HCW (n = 8) had to all other HCW in the PICU of the children’s hospital (n = 49) before sick leave. Nodes in the network each represent one HCW of the PICU for each day (from 1st to 30th of March). The shape of each node represents whether the HCW worked that day (triangle) or not (circle) or was tested positive for COVID-19 over the course of March (X). HCWs that were not on duty are colored in a light gray. The color of nodes represents whether the HCW was tested positive (red) or negative (green) for COVID-19 that day and if the HCW showed symptoms (yellow framing). HCWs worked in shifts. Edges in the plot represent simultaneous presence in the ward either due to duty on the same shift or to time-wise overlapping presence in the ward. The color of the edges shows if the contact between HCWs was with (blue) or without (magenta) extra containment measures.

From the PICU population at risk (49), an infection rate of 16.3% was calculated. With a total of 59 registered cases in the regional district of the children’s hospital on March 18, the PICU accounted for 12% of those reported numbers. In addition, all current and recent patients of the ward were screened. Patients were tested every second day for a total of 14 days if they had been in contact with one of the infected HCWs. Fortunately, none of the patients were diagnosed positive. Noteworthy, no COVID-19 patient was treated during the time of the reported outbreak. Hence, transmission into the PICU was community acquired. Patients were excluded of further calculations and statistics.

Symptoms and Viral Persistence

From the 91 HCWs screened subsequently, 45% reported symptoms corresponding to characteristics of COVID-19 clinical presentation.4 From those reporting symptoms, only 19.5% were actually SARS-CoV-2 positive.

Symptoms duration among our positive cases was up to 21 days and clinical presentation was, overall, highly variable (Table 1). In fact, 37.5% of the positive HCWs did not develop any fever, highlighting the fact that fever alone is not suitable for screening as already reported elsewhere.5 Instead, coughing was reported at least for some days in all cases. Rhinitis, myalgia and sore throat were as common as fever. All experienced mild to moderate disease; none of the HCWs’ disease conditions required hospitalization.

TABLE 1. - Basic Statistics of the Children’s Hospital and the PICU, Numbers of HCWs, PCR-Screening Tests and Basic Time Rates
Children’s Hospital PICU
N % N %
HCWs 432 56
Female:male 8:1 4.6:1
PCR screening
Total number of tests 578 171
Contact/symptomatic HCWS (March) 102 23.6% 49 87.5%
Total number of HCWs tested (March) 91 21% 38 77.5%
Screened symptomatic HCWs (March) 41 45% 14 36.8%
HCWs in mass screening 316 73% 39 69.6%
SARS-CoV-2 positive HCWs 9 2% 8 16.3%
Median Range Median Range
Age at diagnosis (y) 28.5 24.3–51.5
Duration of virus persistence (d) 23 10–33
Time from exposure to symptoms (d) 6 3–17
Time from exposure to diagnosis (d) 14 4–17
Duration of symptoms (d) 19.5 6–39

Regarding the incubation period in our cohort, time from potential first contact with our symptomatic index HCW (ID 35) to symptom development ranged between 6 to 39 days, to positive test result from 4 to 17 days.

Nasopharyngeal samples remained positive for SARS-CoV-2 RNA for a median of 23 days after the first positive test. Remarkably, we noticed a high variation in the time period of viral persistence and an intraindividual fluctuation of positive and negative results.

Mass Screening

One month after the outbreak, from April 14 to April 27, we performed a mass screening of 316 HCWs of the children’s hospital (73%). Despite increasing case numbers in Germany only 1 additional case was detected. This HCW had no contact with the PICU and most likely acquired SARS-CoV-2 in the community. From the previously positive cases, only 1 (ID 31) was still weakly positive, while reporting no symptoms, and 1 HCW (ID 47) was still reporting symptoms of a dry cough.


We experienced a SARS-CoV-2 outbreak among the HCWs of our PICU with an infection rate of 16.3%. The outbreak was noticed between the diagnosis of the first symptomatic HCW on March 13 and March 23 with the positive testing of the eighth HCW. Transmission only occurred within the PICU, despite multiple contacts to HCWs of other departments of the children’s hospital.

SARS-CoV-2-infection is mainly transmitted through droplets generated by coughing, sneezing or close contact to infected individuals.6 In our setting, we postulate that most transmissions occurred via droplets and “unprotected” close contact. After the implementation of protected close contact, the transmission was terminated. We therefore conclude that simple surgical face masks and physical distancing can actively reduce the number of transmissions in a hospital setting. This effectiveness has already been described during the 2004 SARS pandemic,7 and the wearing of face masks concept is emphasized by the fact that a-/presymptomatic infected persons can transmit the virus unknowingly.8

Sensitive and early recognition of SARS-CoV2 in HCWs is essential for the hospital infection prevention strategy.9,10 In our setting, the utilization of a point-of-care testing machine lead to the swift detection of a positive HCW directly within the PICU. By this, strict hygiene measures and subsequential screening of all persons at risk could be implemented without delay. Thus, early and rapid diagnostics are crucial to avoid further spread of the virus.

With the help of early identification of infected personnel, the operability of the entire intensive care unit was maintained. In addition, unnecessary quarantine of uninfected and healthy staff members was avoided. Furthermore, it is very important to highlight that only 19.5% of the personnel presenting COVID19-like symptoms were actually SARS-CoV-2 positive. In consequence, excluding all symptomatic HCWs from work would have been sending 80% into unnecessary quarantine. On the other hand, it should also be noticed that positive asymptomatic cases have been reported,8 which moreover emphasizes the need to implement screening algorithms not only based on reported symptoms. Fever, often used as a cardinal symptom, may not be an appropriate indication for SARS-CoV2 infection, as evidenced in our cohort where 38% of positive cases did not present with fever at all.

Despite the limited number of individuals involved in the outbreak reported herein, the relevance of this report is documented by the ability to control the viral spreading while maintaining operability of the entire ICU. Thus, this report should encourage healthcare providers to continue their service, even when HCWs present with mild respiratory symptoms, given that unprotected face-to-face contact is avoided and rapid diagnostics are available. Positive SARS-CoV-2 results will then, in any case, lead to relieve of duty and quarantine.

First and foremost, the introduction of SARS-CoV-2 in patients was avoided and the normal functionality of PICU was guaranteed.


The outbreak led to the spontaneous analysis and implementation of containment measures. In our setting, following of hygiene measures such as the permanent use of surgical masks and limiting interpersonal contact stopped the outbreak. In addition, the necessity of point-of-care testing was demonstrated to swiftly track an internal outbreak. Moreover, interpersonnel contact tracing among HCWs can provide significant information to stop the virus from spreading. Importantly, symptomatic and asymptomatic personnel were screened likewise.

We were able to contain a large outbreak of SARS-CoV-2 infection in our PICU due to simple and cost-effective means. Most valuable, routine medical care for the critically ill children and adolescents could be continued.


We want to thank the whole PICU-team for their ongoing support, motivation and working effort in the care of critically ill children, also in the face of the current pandemic and under complicated circumstances. Without the daily commitment, this work would not have been possible. Our thanks to the diseased HCWs, who voluntarily shared their data.


1. Polke-Majewski K. Weggesperrt im Hotel. Zeit on line. 2020Accessed April 9, 2020
2. Kluytmans M, Buiting A, Pas S, et al. SARS-CoV-2 infection in 86 healthcare workers in two Dutch hospitals in March 2020. medRxiv. 2020. 2020.03.23.20041913. doi: 10.1101/2020.03.23.20041913
3. Ferioli M, Cisternino C, Leo V, et al. Protecting healthcare workers from SARS-CoV-2 infection: practical indications. Eur Respir Rev. 2020; 29:200068
4. Zheng Y, Xu H, Yang M, et al. Epidemiological characteristics and clinical features of 32 critical and 67 noncritical cases of COVID-19 in Chengdu. J Clin Virol. 2020; 127:104366
5. Danis K, Epaulard O, Bénet T, et al. Cluster of coronavirus disease 2019 (Covid-19) in the French Alps, 2020. Clin Infect Dis. 2020; 71:825–832
6. Xu R, Cui B, Duan X, et al. Saliva: potential diagnostic value and transmission of 2019-nCoV. Int J Oral Sci. 2020; 12:11
7. Jefferson T, Del Mar CB, Dooley L, et al. Physical interventions to interrupt or reduce the spread of respiratory viruses. Cochrane Database Syst Rev. 2011; 2011:CD006207
8. Bai Y, Yao L, Wei T, et al. Presumed asymptomatic carrier transmission of COVID-19. JAMA. 2020; 323:1406–1407
9. Hoe Gan W, Wah Lim J, Koh D. Preventing intra-hospital infection and transmission of COVID-19 in healthcare workers. Saf Health Work. 2020; 11:241–243
10. Folgueira MD, Munoz-Ruiperez C, Alonso-Lopez MA, et al. SARS-CoV-2 infection in health care workers in a large public hospital in Madrid, Spain, during March 2020. medRxiv. 2020. 2020.04.07.20055723. doi: 10.1101/2020.04.07.20055723

SARS-CoV-2; containment measures; healthcare workers; pediatric intensive care unit; outbreak

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