Multiplex PCR analysis of clusters of unexplained viral respiratory tract infection in Cambodia

Enterovirus D68 in Viet Nam (2009-2015)

BACKGROUND

Since 1962, enterovirus D68 (EV-D68) has been implicated in multiple outbreaks and sporadic cases of respiratory infection worldwide, but especially in the USA and Europe with an increasing frequency between 2010 and 2014. We describe the detection, associated clinical features and molecular characterization of EV-D68 in central and southern Viet Nam between 2009 and 2015.

METHODS

Enterovirus/rhinovirus PCR positive respiratory or CSF samples taken from children and adults with respiratory/central nervous system infections in Viet Nam were tested by an EV-D68 specific PCR. The included samples were derived from 3 different observational studies conducted at referral hospitals across central and southern Viet Nam between 2009 and 2015. Whole-genome sequencing was carried out using a MiSeq based approach. Phylogenetic reconstruction and estimation of evolutionary rate and recombination were carried out in BEAST and Recombination Detection Program, respectively.

RESULTS

EV-D68 was detected in 21/625 (3.4%) enterovirus/rhinovirus PCR positive respiratory samples but in none of the 15 CSF. All the EV-D68 patients were young children (age range: 11.8 - 24.5 months) and had moderate respiratory infections. Phylogenetic analysis suggested that the Vietnamese sequences clustered with those from Asian countries, of which 9 fell in the B1 clade, and the remaining sequence was identified within the A2 clade. One intra sub-clade recombination event was detected, representing the second reported recombination within EV-D68. The evolutionary rate of EV-D68 was estimated to be 5.12E ^-3 substitutions/site/year. Phylogenetic analysis indicated that the virus was imported into Viet Nam in 2008.

CONCLUSIONS

We have demonstrated for the first time EV-D68 has been circulating at low levels in Viet Nam since 2008, associated with moderate acute respiratory infection in children. EV-D68 in Viet Nam is most closely related to Asian viruses, and clusters separately from recent US and European viruses that were suggested to be associated with acute flaccid paralysis.

Enterovirus D68 in Viet Nam (2009-2015)

Background: Since 1962, enterovirus D68 (EV-D68) has been implicated in multiple outbreaks and sporadic cases of respiratory infection worldwide, especially in the USA and Europe with an increasing frequency between 2010 and 2014. We describe the detection, associated clinical features and molecular characterization of EV-D68 in central and southern Viet Nam between 2009 and 2015.

Methods: Enterovirus/rhinovirus PCR positive respiratory or CSF samples taken from children and adults with respiratory/central nervous system infections in Viet Nam were tested by an EV-D68 specific PCR. The included samples were derived from 3 different observational studies conducted at referral hospitals across central and southern Viet Nam 2009  2015. Whole-genome sequencing was carried out using a MiSeq based approach. Phylogenetic reconstruction and estimation of evolutionary rate and recombination were carried out in BEAST and Recombination Detection Program, respectively.

Results: EV-D68 was detected in 21/625 (3.4%) enterovirus/rhinovirus PCR positive respiratory samples but in none of the 15 CSF. All the EV-D68 patients were young children (age range: 11.8 – 24.5 months) and had moderate respiratory infections. Phylogenetic analysis suggested that the Vietnamese sequences clustered with those from Asian countries, of which 9 fell in the B1 clade, and the remaining sequence was identified within the A2 clade. One intra sub-clade recombination event was detected, representing the second reported recombination within EV-D68. The evolutionary rate of EV-D68 was estimated to be 5.12E ^-3 substitutions/site/year. Phylogenetic analysis indicated that the virus was imported into Viet Nam in 2008.

Conclusions: We have demonstrated for the first time EV-D68 has been circulating at low levels in Viet Nam since 2008, associated with moderate acute respiratory infection in children. EV-D68 in Viet Nam is most closely related to Asian viruses, and clusters separately from recent US and European viruses that were suggested to be associated with acute flaccid paralysis.

Enterovirus D68 and Human Respiratory Infections

Enterovirus D68 (EV-D68) is a member of the species Enterovirus D in the genus Enterovirus of the Picornaviridae family. EV-D68 was first isolated in the United States in 1962 and is primarily an agent of respiratory disease. Infections with EV-D68 have been rarely reported until recently, when reports of EV-D68 associated with respiratory disease increased notably worldwide. An outbreak in 2014 in the United States, for example, involved more than 1,000 cases of severe respiratory disease that occurred across almost all states. Phylogenetic analysis of all EV-D68 sequences indicates that the circulating strains of EV-D68 can be classified into two lineages, lineage 1 and lineage 2. In contrast to the prototype Fermon strain, all circulating strains have deletions in their genomes. Respiratory illness associated with EV-D68 infection ranges from mild illness that just needs outpatient service to severe illness requiring intensive care and mechanical ventilation. To date, there are no specific medicines and vaccines to treat or prevent EV-D68 infection. This review provides a detailed overview about our current understanding of EV-D68-related virology, epidemiology and clinical syndromes, pathogenesis, and laboratory diagnostics.

Global emergence of enterovirus D68: a systematic review

Since its discovery in California in 1962, reports of enterovirus D68 have been infrequent. Before 2014, infections were confirmed in only 699 people worldwide. In August, 2014, two paediatric hospitals in the USA reported increases in the number of patients with severe respiratory illness, with an over-representation in children with asthma. Shortly after, the authorities recognised a nationwide outbreak, which then spread to Canada, Europe, and Asia. In 2014, more than 2000 cases of enterovirus D68 were reported in 20 countries. Concurrently, clusters of children with acute flaccid paralysis of unknown cause were reported in several US states and in Europe. Enterovirus D68 infection was confirmed in some of the paralysed children, but not all. Complications in patients who were severely neurologically affected resemble those caused by poliomyelitis. In this paper we systematically review reports on enterovirus D68 to estimate its global epidemiology and its ability to cause respiratory infections and neurological damage in children. We extracted data from 70 papers to report on prevalence, symptoms, hospitalisation and mortality, and complications of enterovirus D68, both before and during the large outbreak of 2014. The magnitude and severity of the enterovirus D68 outbreak underscores a need for improved diagnostic work-up of paediatric respiratory illness, not only to prevent unnecessary use of antibiotics, but also to ensure better surveillance of diseases. Existing surveillance systems should be assessed in terms of capacity and ability to detect and report any upsurge of respiratory viruses such as enterovirus D68 in a timely manner, and focus should be paid to development of preventive measures against these emerging enteroviruses that have potential for severe disease.