Until fairly recently, members of the family Picornaviridae, genus Cardiovirus, species Cardiovirus B [8] were thought to mainly replicate in the gut of rodents[1].

But in 2007 the genome of Saffold virus (SAFV-1) was deduced from a stool specimen of a human infant with fever[2].

There are now at least eleven genotypes of human cardioviruses identified, and this is increasing [3, 4] but epidemiology for all cardioviruses is patchy.

One small study found SAFV most frequently during summer and early fall.[5] SAFV-1 has also been found in the stools of children with diarrhoea in China, although co-detections of rotavirus or norovirus were made in all cases[5].

SAFV-2 was the sole virus identified in nasopharyngeal aspirates from children with fever, otitis media or pneumonia.[6] SAFV-2 grows better in LLC-MK2 cells[6] suggesting variation in tropism compared to SAFV-1, possibly related to receptor usage. SAFV-3 was identified in the stools of two one-year old children with acute gastroenteritis (AGE) [7] and also isolated from the stools of a one year-old in the Netherlands using HeLa cells, permitting the first serosurvey of a SAFV.[2]

SAFV-2 was found to be a global and ubiquitous virus with seroprevalence reaching >90% by two years of age despite low PCR prevalence (<1%).[2, 3, 6] The VP1 protein has proven a useful PCR target to discriminate SAFV genotypes from variants of the same type.[2]

An apparent absence of symptoms from some infections had led some to suggest that the human cardioviruses are orphan viruses [2, 5] with no recognised disease association.

In 2008 a genetically distinct cardiovirus was identified in the respiratory tract of a child with influenza-like illness[1]. Subsequently six other detections were made from the stools of different children under two years of age, with AGE. The detections were of related but mostly distinct viruses, putatively called human TMEV-like Cardiovirus (HTCV)[1], but sharing >90% amino acid (~80% nucleotide) identity with SAFV-2. Half of the HTCV detections were made in the presence of another virus, again making it difficult to identify an aetiology within the gut for these viruses[1]. A small number of respiratory specimens were screened but no detections were made.

NOTE: This is derived from a failed 2010 grant application.

References…

1. Identification of cardioviruses related to Theiler’s murine encephalomyelitis virus in human infections
   http://www.pnas.org/content/105/37/14124.abstract
2. Saffold virus, a human Theiler’s-like cardiovirus, is ubiquitous and causes infection early in life
   http://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1000416
   
3. Discovery of a novel human picornavirus in a stool sample from a pediatric patient presenting with fever of unknown origin
   http://jcm.asm.org/content/45/7/2144.short
   
4. Frequent detection of highly diverse variants of cardiovirus, cosavirus, bocavirus, and circovirus in sewage samples collected in the United States
   http://jcm.asm.org/content/47/11/3507.full
   
5. New Saffold cardiovirus in children, China
   https://www.ncbi.nlm.nih.gov/pubmed/19523321
   
6. New Saffold cardioviruses in 3 children, Canada
   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2600268/
   
7. Circulation of 3 lineages of a novel Saffold cardiovirus in humans
   https://wwwnc.cdc.gov/eid/article/14/9/08-0570_article
   
8. https://talk.ictvonline.org/ictv-reports/ictv_online_report/positive-sense-rna-viruses/picornavirales/w/picornaviridae/678/genus-cardiovirus