We investigated the kinetics of the Middle East respiratory syndrome coronavirus (MERS-CoV) neutralizing and spike protein antibody titers over the course of 1 year in 11 patients who were confirmed by reverse transcription PCR to have been infected during the outbreak in South Korea in 2015. Robust antibody responses were detected in all survivors who had severe disease; responses remained detectable, albeit with some waning, for <1 year. The duration of viral RNA detection (but not viral load) in sputum significantly correlated with the antibody response magnitude. The MERS S1 ELISA antibody titers correlated well with the neutralizing antibody response. Antibody titers in 4 of 6 patients who had mild illness were undetectable even though most had evidence of pneumonia. This finding implies that MERS-CoV seroepidemiologic studies markedly underestimate the extent of mild and asymptomatic infection. Obtaining convalescent-phase plasma with high antibody titers to treat MERS will be challenging.

No potential conflict of interest relevant to this letter was reported. The authors reply: Campochiaro and Caruso are correct that mention of cardiovascular associations with ankylosing spondylitis and axial spondyloarthritis, including specific conductionsystem lesions and aortic-root lesions, was largely absent from our review of spondyloarthritis. These specific lesions are uncommon and tend to occur late in the disease course, as does the other more common but less specific cardiovascular illness mentioned in their letter. The focus of our article was on early diagnosis and clinical management of the axial disease, and this priority, along with space and citation limitations, precluded our describing specific cardiovascular manifestations. Rudwaleit M, van derRudwaleit and colleagues make the important point that diagnosis in clinical practice cannot be based solely on fulfillment of classification criteria. We tried to make this point in the article, but perhaps our wording conveyed some unintended ambiguity. In order to introduce the new concept of axial spondyloarthritis, we described the classification criteria for this entity proposed by the ASAS in 2009. In discussing this concept, including the critical role of MRI, we referred to this entity as a diagnosis, in the sense of its being a defined medical condition. We did not intend by this to imply that one can rely strictly on these criteria to establish a diagnosis in clinical practice. In fact, we stated explicitly, "These classification criteria have limited use outside the arena of clinical research," to introduce the algorithm (in Fig. 2 of our article) for use in clinical practice.The algorithm itself is a modification of one published by the correspondents and their colleagues, 1 but it was modified specifically to further emphasize the importance of weighing clinical data and post-test probabilities 2 and of applying clinical judgment to the diagnostic process. Moreover, the discussion of MRI findings includes mention of lesions that are not part of the classification criteria but that can be helpful in supporting a diagnosis in clinical practice. Finally, the Summary section in our article reemphasizes the potential difficulty in accurately establishing or ruling out a diagnosis of axial spondyloarthritis, with no mention of criteria. Viral Load Kinetics of MERS Coronavirus InfectionTo the Editor: The outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) infection in South Korea involved 186 patients and resulted in 38 deaths, with four large hospital outbreaks accounting for 82% of the total cases. 1,2 Here, we report changes in viral load over time in patients with MERS.We included all patients who were admitted to three Seoul National University-affiliated hospitals; the institutional review boards of these hospitals approved this study and waived the need for written informed consent on public health grounds. The patients were categorized into a group with severe disease (severe group) or a group with mild disease (mild grou...

BackgroundFrom May to July 2015, the Republic of Korea experienced the largest outbreak of Middle East respiratory syndrome (MERS) outside the Arabian Peninsula. A total of 186 patients, including 36 deaths, had been diagnosed with MERS-coronavirus (MERS-CoV) infection as of September 30th, 2015.Materials and MethodsWe obtained information of patients who were confirmed to have MERS-CoV infection. MERS-CoV infection was diagnosed using real-time reverse-transcriptase polymerase chain reaction assay.ResultsThe median age of the patients was 55 years (range, 16 to 86). A total of 55.4% of the patients had one or more coexisting medical conditions. The most common symptom was fever (95.2%). At admission, leukopenia (42.6%), thrombocytopenia (46.6%), and elevation of aspartate aminotransferase (42.7%) were observed. Pneumonia was detected in 68.3% of patients at admission and developed in 80.8% during the disease course. Antiviral agents were used for 74.7% of patients. Mechanical ventilation, extracorporeal membrane oxygenation, and convalescent serum were employed for 24.5%, 7.1%, and 3.8% of patients, respectively. Older age, presence of coexisting medical conditions including diabetes or chronic lung disease, presence of dyspnea, hypotension, and leukocytosis at admission, and the use of mechanical ventilation were revealed to be independent predictors of death.ConclusionThe clinical features of MERS-CoV infection in the Republic of Korea were similar to those of previous outbreaks in the Middle East. However, the overall mortality rate (20.4%) was lower than that in previous reports. Enhanced surveillance and active management of patients during the outbreak may have resulted in improved outcomes.

Middle East Respiratory Syndrome coronavirus (MERS-CoV) was first isolated from a patient with severe pneumonia in 2012. The 2015 Korea outbreak of MERSCoV involved 186 cases, including 38 fatalities. A total of 83% of transmission events were due to five superspreaders, and 44% of the 186 MERS cases were the patients who had been exposed in nosocomial transmission at 16 hospitals. The epidemic lasted for 2 months and the government quarantined 16,993 individuals for 14 days to control the outbreak. This outbreak provides a unique opportunity to fill the gap in our knowledge of MERS-CoV infection. Therefore, in this paper, we review the literature on epidemiology, virology, clinical features, and prevention of MERS-CoV, which were acquired from the 2015 Korea outbreak of MERSCoV.

We investigated the kinetics of serologic responses to Middle East respiratory syndrome coronavirus (MERS-CoV) infection by using virus neutralization and MERS-CoV S1 IgG ELISA tests. In most patients, robust antibody responses developed by the third week of illness. Delayed antibody responses with the neutralization test were associated with more severe disease.