Dear Editor,
A 2015–2016 surveillance study in Saudi Arabia on Middle East Respiratory Syndrome
Coronavirus (MERS-CoV) infections showed that cases of influenza infections were much
more common than those of MERS-CoV [1]. These findings indicate that travelers planning
to visit MERS-CoV affected countries should be vaccinated against influenza virus.
Here, we describe the results from a 2016 and 2017 surveillance study in the most
populous province in Korea, the Gyeonggi province (population: 25.5 million; area:
11,730 km2), and we demonstrate the Korean public health effort to prevent local transmission
of MERS-CoV. In 2015, the Republic of Korea experienced a large outbreak of MERS-CoV
with 186 laboratory-confirmed cases [2]. In this outbreak, inter-hospital and intra-hospital
transmission were determination factors of the MERS-CoV infections [2]. After the
outbreak, a Korean national surveillance program with virological testing for MERS-CoV
and other respiratory viruses was implemented to rapidly identify infected travelers
returning from MERS-CoV-affected countries.
Each suspected case of MERS-CoV was defined as a person who had a lower respiratory
tract illness (a cough, sputum or shortness of breath), fever (over 37.8 °C), and
an epidemiological link to recent travel (within the past 14 days) to a MERS-CoV-affected
country [3]. The demographic and clinical information for suspected cases were collected
through patient interviews [3].
Public health officers immediately transferred suspected cases by ambulance to a negative
pressure room in an isolation ward of a designated hospital. The officers were equipped
with personal protective equipment including disposable coveralls, nitrile gloves,
N95 particulate half-masks with a two-strap design, unvented goggles, and boots. Upper
and lower respiratory specimens (nasopharyngeal, oropharyngeal swab and sputum) and
blood samples of individuals with a suspected infection were immediately collected
and transported at 4 °C to the provincial public health laboratory [3]. The delay
from the report of the onset of symptoms and notification of the public health authority,
to the quarantine time including self-isolation, was recorded.
To identify MERS-CoV, qualitative Real-time Reverse Transcription-Polymerase Chain
Reaction (rRT-PCR) testing was performed using the TaqMan method by targeting regions
upstream of the envelope (UpE) and the open reading frame 1a gene [4]. A cycle of
threshold value ≤ 37 was regarded as positive [4]. Additional rRT-PCR using respiratory
swabs was conducted to identify other respiratory viruses including influenza (IFV;
A, B), human respiratory syncytial virus (hRSV; A, B), human metapneumovirus (hMPV;
A, B), human parainfluenza virus (hPIV; I, II, III), human adenovirus (hAdV), human
bocavirus (hBoC), human rhinovirus (hRV), and human coronavirus (hCoV; 229E, OC43,
NL63). Table 1
shows the characteristics of the suspected cases. There were 56 male cases among 99
suspected cases. Seven of the suspected cases had underlying disease (either hypertension
or diabetes, or both). The median age of the suspected case group was 43 years (range,
1 to 70; mean, 42.3); and the group had a median of 11 contacts (range, 1 to 33; mean,
21.2). The median delay between the onset of symptoms and the notification of the
public health authority was 30 hours (range, 0–240 hrs; mean, 21 hrs). In addition,
the median time interval was 1.0 hour (range, 0–63 hrs; mean, 3.4 hrs) between notification
and patient quarantine of case, and it was 35 hours (range, 2–240 hrs; mean, 53 hrs)
between the onset of symptoms and patient quarantine.
Table 1
Characteristics of suspected cases of Middle East Respiratory Syndrome Coronavirus
infections (n = 99).
Table 1
Number (%)
Sex
Male
56 (56.6)
Female
43 (43.4)
Age groups, years
0–18
9 (9.1)
19-65
77 (77.8)
>65
13 (13.1)
Nationality
Korean
94 (94.9)
Saudi Arabian
2 (2.0)
UAE
2 (2.0)
Pakistani
1 (1.0)
Interval of public health responsea
<1 hours
62 (62.6)
1 ― < 2 hours
11 (11.1)
2 ― < 3 hours
7 (7.0)
3 ― < 4 hours
4 (4.0)
>5 hours
15 (15.2)
a
The time interval between notification of public health authority and the quarantine
of suspected case.
In comparison with the United Kingdom (UK), the delay in time between the initiation
of symptoms and patient quarantine for the Republic of Korea was relatively shorter
(median duration of symptoms and sample testing in UK: 5 days, range: 1–22 days) [5].
In addition, the detection rate of other respiratory virus pathogens was 66.3%, which
is higher than reported for the UK (50.3%) [5]. All the specimens obtained during
the study were confirmed as MERS-CoV negative. However, a viral etiology was detected
in 66 (66%) of the cases as follows: Influenza A H3N2 (23 suspected patients, 23%),
hRSV (12, 12%), Influenza B (11, 11%), Influenza A H1N1 (10, 10%), hMPV (7, 7%), hCoV
(5, 5%), hAdV (3, 3%), hPIV II (1, 1%), and hBoC (1, 1%). Thus, influenza vaccination
prior to travel may benefit individual travelers and save the public health resources.
In addition to the above data, it has been found that a significant fraction of confirmed
MERS-CoV cases in previous outbreaks has been linked to issues related to healthcare
setting (99%; Republic of Korea in 2015, 43%; Jeddah, Saudi Arabia in 2014) [2,6].
Therefore, the continuous and immediate public health response after symptom onset
in a suspected case prior to the patient's visit to a health-care facility is important.
Since MERS-CoV infection has a wide spectrum of illness from asymptomatic to severe,
some potential cases could have been missed. However, no additional cases from the
Gyeonggi Province hospitals have been reported through the Severe Acute Respiratory
Infection surveillance network.
In this study, although no cases of MERS-CoV infection were identified in the Gyeonggi
Province, Korea, cases of influenza infection were dominant. It remains important
for the risk of the importation of MERS-CoV to be reduced through the continued surveillance
of travelers returning from MERS-CoV affected countries combined with a rapid public
health response. In addition, vaccination against influenza for the travelers prior
to their travel should be considered.