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Commentary
MERS-CoV
Asymptomatic Health Care Workers In Italy
Recombinomics
Commentary 12:45
June 4, 2013
The above translation provides additional detail on the 10 asymptomatic contacts who have tested positive for MERS-CoV in Florence, Italy (see map). The above health care workers (HCWs) included doctors and nurse who had contacts with the index case at the two facilities which treated the confirmed case (45M) who had returned to Italy from Jordan. Two contacts (his niece, 2F, and a co-worker, 42F) developed symptoms and tested positive. However, Italy expanded testing to asymptomatic contacts and positives were detected in samples from the upper respiratory tract (nasopharyngeal swabs). Thus, the key difference between the asymptomatic positives detected in Italy and negatives cited elsewhere are linked to the timing of the testing.
In the Middle east, most cases have developed pneumonia and are hospitalized. These cases have a high viral load and are usually fatal. Those that survive have pneumonia are generally are severe cases. Contacts are monitored but not tested.
Others, such as France, have tested mild contacts, but the testing is when the patients have largely recovered and MERS=CoV has been cleared. Thus, in France the symptomatic HCWs were released as soon as they tested negative, because they had already recovered from their illness. Similarly, the symptomatic HCWs associated with MERS-CoV cases in England and Germany were also tested long after they developed symptoms.
The most striking example was the daughter of the index case in England who developed symptoms while performing Umrah in Saudi Arabia. He had been infected with MERS-CoV and H1N1pdm09. His son and sister, who had not traveled outside of England developed symptoms and were positive for MERS-CoV and type 2 parainfluenza virus (HPIV-2). They developed symptoms within 1 day of each other and gad no recent contact with each other. The Health Protection Agency initially suggested that another family member was responsible for the infection of the sister since she had no contact with her nephew and had limit contact with the index case. The daughter of the index case, who also traveled to Saudi Arabia was “cleared” through testing, suggesting she had had mild symptoms. Moreover, two contacts were HPIV-2 positive but MERS-CoV negative suggesting she was one of the contacts who had been infected with both viruses but had clear MERS-CoV when samples were collected for testing.
Moreover, the ealriest MERS-CoV cases were in Jordan over a year ago. Although the milder cases were classified as "probable" because of the lack of sample, the disese onset dates strongly support human to human transmission among the ICU HCWs, with strong similaritys with SARS-CoV transission in 2003.
Similarly, mild contacts of the case in Tunisia were quickly tested and were MERS-CoV confirmed.
Thus, the chief difference between the MERS-CoV positives in mild / asymptomatic cases, and those tested elsewhere has been the timing of sample collection. The results in Italy suggested the viral load in mild cases is confined to the upper respiratory tract, which is cleared, and testing of samples collected when the patient has largely recovered yields negative results.
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