Replies

Suspected SARS - Germany ex Singapore via New York:

Paramyxovirus-like particles identified by electron microscopy

Numerous tests have been performed on the 3 patients admitted on
Saturday 15 March to the Isolation Unit at Frankfurt am Main with suspected severe acute respiratory syndrome (SARS). Tests from respiratory specimens for influenza A and B virus, respiratory syncytial virus, enteroviruses, _Mycoplasma pneumoniae_ and _Chlamydia_ spp. by antigen enzyme linked immunosorbent assay (ELISA) and/or polymerase chain reaction (PCR) were all negative; antibody tests for dengue, influenza A and B, measles, hantaviruses, _Mycoplasma pneumoniae_ and _Chlamydia_ spp. were likewise negative or unremarkable so far; further test results are pending.

Particles morphologically resembling paramyxoviruses were seen in respiratory specimens (throat swab and sputum) obtained from the index patient, a doctor from Singapore, by the teams in Marburg and in Frankfurt am Main.

It remains to be seen whether this finding can be confirmed -- tests including low-stringency paramyxovirus PCR and tissue culture are currently under way in Hamburg, in Marburg and in Frankfurt am Main. It needs to be emphasised that at this time these preliminary results only indicate a suspicion. Furthermore, even if the presence of a paramyxovirus was confirmed, it is not clear at this stage whether this might represent the causal agent of SARS or rather a coincidental finding.

Preiser's caution on the interpretation of these results is paramount here: "It needs to be emphasised that at this point of time these preliminary results only indicate a suspicion. Furthermore, even if the presence of a paramyxovirus was confirmed, it is not clear at this stage whether this might represent the causal agent of SARS or rather a coincidental finding."

Confirmation of these findings will be important as well as identification of a similar agent from additional cases of SARS will be necessary before it can be concluded that this agent is the etiology of SARS. - Mod.MPP]

[Paramyxoviruses are viruses associated predominantly with respiratory infections (the parainfluenza viruses, and respiratory syncytial virus (RSV)) and common childhood illnesses (mumps and measles).

Some of these viruses are ubiquitous (in particular human RSV) and it would not be exceptional to detect one of these viruses fortuitously by electron microscopy in any virus screening exercise. In general, paramyxoviruses only infect vertebrates and no arthropod vectors are known.

Unexpectedly, in recent years several new paramyxoviruses have been discovered. Predominant among these are _Hendra virus_ and _Nipah virus_, 2 related viruses isolated from bats in Australia and South East Asia, which have been responsible for outbreaks of severe disease in the human population. These two viruses differ significantly from other paramyxoviruses in molecular terms and might not be detected by PCR without the use of specific primers.

Other novel paramyxoviruses of unknown pathogenic potential are _Salem virus_, isolated from a horse in North America, _Tupaia paramyxovirus_, isolated from a tree shrew (_Tupaia_ sp.) in Thailand, and a heterogeneous collection of paramyxoviruses isolated from snakes, lizards, and turtles. Perhaps the most surprising discovery was the recent characterization of a novel pneumovirus (that is, a member of the sub-family _Pneumovirinae_ of the family _Paramyxoviridae)), designated _Human metapneumovirus_, which is associated with respiratory illness in infancy worldwide. Consequently a novel paramyxovirus must rank high among candidates for the etiologic agent of SARS. - Mod.CP]