PMC:5968208 / 10023-15063 JSONTXT

{"project":"2_test","denotations":[{"id":"29656631-27272273-28528120","span":{"begin":481,"end":483},"obj":"27272273"},{"id":"29656631-27475739-28528121","span":{"begin":849,"end":851},"obj":"27475739"},{"id":"29656631-26584223-28528122","span":{"begin":1015,"end":1017},"obj":"26584223"},{"id":"29656631-23718156-28528123","span":{"begin":1235,"end":1237},"obj":"23718156"},{"id":"29656631-24460984-28528124","span":{"begin":1238,"end":1240},"obj":"24460984"},{"id":"29656631-25465252-28528125","span":{"begin":2010,"end":2012},"obj":"25465252"},{"id":"29656631-19704998-28528126","span":{"begin":2016,"end":2018},"obj":"19704998"},{"id":"29656631-23831143-28528127","span":{"begin":2733,"end":2735},"obj":"23831143"},{"id":"29656631-23831143-28528128","span":{"begin":2874,"end":2876},"obj":"23831143"},{"id":"29656631-23831141-28528129","span":{"begin":2877,"end":2879},"obj":"23831141"},{"id":"29656631-26493654-28528130","span":{"begin":3002,"end":3004},"obj":"26493654"},{"id":"29656631-26583829-28528131","span":{"begin":4041,"end":4043},"obj":"26583829"},{"id":"29656631-27332149-28528132","span":{"begin":4305,"end":4307},"obj":"27332149"},{"id":"29656631-17855683-28528133","span":{"begin":4308,"end":4310},"obj":"17855683"}],"text":"DISCUSSION\nLimited information exists regarding MERS-CoV seroprevalence among populations other than confirmed MERS cases. Saudi Arabian data showed that the seroprevalence of MERS-CoV IgG among the general population was 0.15% [25], suggesting that a number of cases of asymptomatic or mild infections may be present in the general population.\nDespite a high prevalence of 186 confirmed MERS cases during the outbreak of MERS in Korea, the rate of asymptomatic infection (1.60%) [15] was lower than expected. The rates of asymptomatic infection confirmed using IFA and PRNT in the present study were 0.06% (1 of 1,610) for all contacts and 0.17% (1 of 574) for patients. These results are markedly lower than the rates of 0.27% (2 of 737) among healthcare workers, and 0.44% (2 of 457) among healthcare workers at MERS-affected hospitals in Korea [16]. Moreover, the rate of asymptomatic or mild infection in Saudi Arabia, the United Arab Emirates, and the Islamic Republic of Iran was approximately 28.00% [12,13,18].\nThe confirmed asymptomatic case presented in this study was a patient at the same hospital as confirmed MERS cases and, unlike in previous studies, was neither an intra-familial infection nor a pediatric infection [26,27]. The low rate of asymptomatic infection in Korea is attributable to the different transmission pathway of MERS infections compared to the Middle East. In Korea, most of the MERS cases were healthcare-associated infections, and none were from an animal. The low asymptomatic infection rate is also attributable to the extensive epidemiological investigation conducted in Korea, including close monitoring of contacts with MERS patients; this helped identify almost all MERS patients. This may also have been attributable to the promotion of proactive identification of patients via mass media and the establishment of communication networks by the government, leading to voluntary reports by people, active quarantine, and countermeasures to this public health crisis [10,28,29].\nELISA is appropriate as a screening tool, as it is 10-fold more sensitive than IFA. However, it may cross-react with seasonal human coronavirus antibodies, so a spike protein-specific IFA is required for confirmation. PRNT is a definitive test when ELISA and IFA have inconclusive results [25]. Only 10% of ELISA-positive results are positive on a neutralization assay [25]. In our study, 1 of 7 patients with borderline or positive ELISA results also had positive results in PRNT. Therefore, the results obtained in our study are accurate because ELISA, IFA, and PRNT were used.\nA previous study predicted the pandemic potential of MERS-CoV to be ≤ 5%; however, this does not indicate that the risk has abated [30]. Prerequisites for reducing the risk include improved surveillance, active contact tracing, and the initiation of animal host searching [30,31]. During the outbreak in Korea, MERS was classified as a notifiable infectious disease and was subjected to surveillance [32]. Since MERS is an imported disease in Korea, it is recommended that precautions be taken before travel and that the time of returning from travel and incubation period be considered.\nThis study showed a low seropositivity in the population of individuals quarantined due to contact with MERS cases. However, there is a possibility that the seropositivity rate was underestimated for the following reasons. Firstly, the participants of the present study were mostly non-healthcare workers and were relatively healthy. Thus, the risk of infection was low. Secondly, the overall participation rate was 48.9%, whereas it was 36.8% in the patient group at a higher risk of infection. Moreover, we only surveyed 10.9% of the quarantined individuals. Therefore, the actual rate of asymptomatic infections may be higher than reported in the present study. Lastly, the present study may have been conducted too late. In a previous study, MERS-CoV ELISA results indicated that the antibody response was highest after 3 weeks from symptom onset [33]. Although no reports have analyzed the duration of antibody presence in MERS patients regardless of symptoms, a recent study of severe acute respiratory syndrome and MERS reported that antibodies in some patients persisted for up to 2-3 years after infection [34,35]. Blood sampling for serologic test in this study was performed on contacts between October and December 2015, while exposure to the confirmed case occurred between May and June 2015 (a gap of 5 months). Thus, a loss of the MERS-CoV antibody titer could have taken place despite actual asymptomatic infections; therefore, the actual rate of asymptomatic infection may be higher than the rate presented in this report.\nIn conclusion, among 1,610 contacts, only 1 non-healthcare worker who was a patient in a MERS-affected hospital had an asymptomatic MERS-CoV infection. To understand new emerging infectious diseases such as MERS, more intensive epidemiologic research is needed, including an analysis of asymptomatic infections."}

{"project":"MyTest","denotations":[{"id":"29656631-27272273-28528120","span":{"begin":481,"end":483},"obj":"27272273"},{"id":"29656631-27475739-28528121","span":{"begin":849,"end":851},"obj":"27475739"},{"id":"29656631-26584223-28528122","span":{"begin":1015,"end":1017},"obj":"26584223"},{"id":"29656631-23718156-28528123","span":{"begin":1235,"end":1237},"obj":"23718156"},{"id":"29656631-24460984-28528124","span":{"begin":1238,"end":1240},"obj":"24460984"},{"id":"29656631-25465252-28528125","span":{"begin":2010,"end":2012},"obj":"25465252"},{"id":"29656631-19704998-28528126","span":{"begin":2016,"end":2018},"obj":"19704998"},{"id":"29656631-23831143-28528127","span":{"begin":2733,"end":2735},"obj":"23831143"},{"id":"29656631-23831143-28528128","span":{"begin":2874,"end":2876},"obj":"23831143"},{"id":"29656631-23831141-28528129","span":{"begin":2877,"end":2879},"obj":"23831141"},{"id":"29656631-26493654-28528130","span":{"begin":3002,"end":3004},"obj":"26493654"},{"id":"29656631-26583829-28528131","span":{"begin":4041,"end":4043},"obj":"26583829"},{"id":"29656631-27332149-28528132","span":{"begin":4305,"end":4307},"obj":"27332149"},{"id":"29656631-17855683-28528133","span":{"begin":4308,"end":4310},"obj":"17855683"}],"namespaces":[{"prefix":"_base","uri":"https://www.uniprot.org/uniprot/testbase"},{"prefix":"UniProtKB","uri":"https://www.uniprot.org/uniprot/"},{"prefix":"uniprot","uri":"https://www.uniprot.org/uniprotkb/"}],"text":"DISCUSSION\nLimited information exists regarding MERS-CoV seroprevalence among populations other than confirmed MERS cases. Saudi Arabian data showed that the seroprevalence of MERS-CoV IgG among the general population was 0.15% [25], suggesting that a number of cases of asymptomatic or mild infections may be present in the general population.\nDespite a high prevalence of 186 confirmed MERS cases during the outbreak of MERS in Korea, the rate of asymptomatic infection (1.60%) [15] was lower than expected. The rates of asymptomatic infection confirmed using IFA and PRNT in the present study were 0.06% (1 of 1,610) for all contacts and 0.17% (1 of 574) for patients. These results are markedly lower than the rates of 0.27% (2 of 737) among healthcare workers, and 0.44% (2 of 457) among healthcare workers at MERS-affected hospitals in Korea [16]. Moreover, the rate of asymptomatic or mild infection in Saudi Arabia, the United Arab Emirates, and the Islamic Republic of Iran was approximately 28.00% [12,13,18].\nThe confirmed asymptomatic case presented in this study was a patient at the same hospital as confirmed MERS cases and, unlike in previous studies, was neither an intra-familial infection nor a pediatric infection [26,27]. The low rate of asymptomatic infection in Korea is attributable to the different transmission pathway of MERS infections compared to the Middle East. In Korea, most of the MERS cases were healthcare-associated infections, and none were from an animal. The low asymptomatic infection rate is also attributable to the extensive epidemiological investigation conducted in Korea, including close monitoring of contacts with MERS patients; this helped identify almost all MERS patients. This may also have been attributable to the promotion of proactive identification of patients via mass media and the establishment of communication networks by the government, leading to voluntary reports by people, active quarantine, and countermeasures to this public health crisis [10,28,29].\nELISA is appropriate as a screening tool, as it is 10-fold more sensitive than IFA. However, it may cross-react with seasonal human coronavirus antibodies, so a spike protein-specific IFA is required for confirmation. PRNT is a definitive test when ELISA and IFA have inconclusive results [25]. Only 10% of ELISA-positive results are positive on a neutralization assay [25]. In our study, 1 of 7 patients with borderline or positive ELISA results also had positive results in PRNT. Therefore, the results obtained in our study are accurate because ELISA, IFA, and PRNT were used.\nA previous study predicted the pandemic potential of MERS-CoV to be ≤ 5%; however, this does not indicate that the risk has abated [30]. Prerequisites for reducing the risk include improved surveillance, active contact tracing, and the initiation of animal host searching [30,31]. During the outbreak in Korea, MERS was classified as a notifiable infectious disease and was subjected to surveillance [32]. Since MERS is an imported disease in Korea, it is recommended that precautions be taken before travel and that the time of returning from travel and incubation period be considered.\nThis study showed a low seropositivity in the population of individuals quarantined due to contact with MERS cases. However, there is a possibility that the seropositivity rate was underestimated for the following reasons. Firstly, the participants of the present study were mostly non-healthcare workers and were relatively healthy. Thus, the risk of infection was low. Secondly, the overall participation rate was 48.9%, whereas it was 36.8% in the patient group at a higher risk of infection. Moreover, we only surveyed 10.9% of the quarantined individuals. Therefore, the actual rate of asymptomatic infections may be higher than reported in the present study. Lastly, the present study may have been conducted too late. In a previous study, MERS-CoV ELISA results indicated that the antibody response was highest after 3 weeks from symptom onset [33]. Although no reports have analyzed the duration of antibody presence in MERS patients regardless of symptoms, a recent study of severe acute respiratory syndrome and MERS reported that antibodies in some patients persisted for up to 2-3 years after infection [34,35]. Blood sampling for serologic test in this study was performed on contacts between October and December 2015, while exposure to the confirmed case occurred between May and June 2015 (a gap of 5 months). Thus, a loss of the MERS-CoV antibody titer could have taken place despite actual asymptomatic infections; therefore, the actual rate of asymptomatic infection may be higher than the rate presented in this report.\nIn conclusion, among 1,610 contacts, only 1 non-healthcare worker who was a patient in a MERS-affected hospital had an asymptomatic MERS-CoV infection. To understand new emerging infectious diseases such as MERS, more intensive epidemiologic research is needed, including an analysis of asymptomatic infections."}