ABSTRACT
The four human coronaviruses (HCoVs) are globally endemic respiratory pathogens. The Middle East respiratory syndrome (MERS) coronavirus (CoV) is an emerging CoV with a known zoonotic source in dromedary camels. Little is known about the origins of endemic HCoVs. Studying these viruses' evolutionary history could provide important insight into CoV emergence. In tests of MERS-CoV-infected dromedaries, we found viruses related to an HCoV, known as HCoV-229E, in 5.6% of 1,033 animals. Human- and dromedary-derived viruses are each monophyletic, suggesting ecological isolation. One gene of dromedary viruses exists in two versions in camels, full length and deleted, whereas only the deleted version exists in humans. The deletion increased in size over a succession starting from camelid viruses via old human viruses to contemporary human viruses. Live isolates of dromedary 229E viruses were obtained and studied to assess human infection risks. The viruses used the human entry receptor aminopeptidase N and replicated in human hepatoma cells, suggesting a principal ability to cause human infections. However, inefficient replication in several mucosa-derived cell lines and airway epithelial cultures suggested lack of adaptation to the human host. Dromedary viruses were as sensitive to the human type I interferon response as HCoV-229E. Antibodies in human sera neutralized dromedary-derived viruses, suggesting population immunity against dromedary viruses. Although no current epidemic risk seems to emanate from these viruses, evolutionary inference suggests that the endemic human virus HCoV-229E may constitute a descendant of camelid-associated viruses. HCoV-229E evolution provides a scenario for MERS-CoV emergence.
Subject(s)
Camelus/virology , Coronavirus Infections/virology , Coronavirus/physiology , Middle East Respiratory Syndrome Coronavirus/physiology , Animals , Base Sequence , Caco-2 Cells , Cell Line , Cell Line, Tumor , Cells, Cultured , Chlorocebus aethiops , Coronavirus/classification , Coronavirus/genetics , Coronavirus Infections/epidemiology , Endemic Diseases , Humans , Kenya/epidemiology , Middle East Respiratory Syndrome Coronavirus/genetics , Phylogeny , Saudi Arabia/epidemiology , Sequence Homology, Nucleic Acid , Vero CellsABSTRACT
A new hepatitis E virus (HEV-7) was recently found in dromedaries and 1 human from the United Arab Emirates. We screened 2,438 dromedary samples from Pakistan, the United Arab Emirates, and 4 African countries. HEV-7 is long established, diversified and geographically widespread. Dromedaries may constitute a neglected source of zoonotic HEV infections.
Subject(s)
Camelus/virology , Hepatitis E virus/genetics , Hepatitis E/veterinary , Africa/epidemiology , Animals , Camelus/blood , Feces/virology , Hepatitis E/blood , Hepatitis E/epidemiology , Hepatitis E/virology , Hepatitis E virus/isolation & purification , Pakistan/epidemiology , Phylogeny , United Arab Emirates/epidemiologyABSTRACT
To analyze the distribution of Middle East respiratory syndrome coronavirus (MERS-CoV)-seropositive dromedary camels in eastern Africa, we tested 189 archived serum samples accumulated during the past 30 years. We identified MERS-CoV neutralizing antibodies in 81.0% of samples from the main camel-exporting countries, Sudan and Somalia, suggesting long-term virus circulation in these animals.
