5 Monivong Boulevard, P.O Box. 983, Phnom Penh, Cambodia [email protected]

Many viruses can be responsible for respiratory diseases: Rhinoviruses, adenovirus, SARS-Coronavirus, MERS-coronaviruses, Influenzaviruses, etc..

IPC is conducting research activities on all these viruses, with a priority on Influenzaviruses as the Cambodian National Influenza Centre and H5 Reference Laboratory. Diagnosis, surveillance and research activities are conducted in close collaboration with other institutes and centers from Cambodian Ministry of Health (MoH) and Ministry of Agriculture, Forestry and Fisheries (MAFF). Influenza virus belongs to the Orthomyxoviridae family of enveloped, segmented negative stranded RNA viruses. There are three types of influenza viruses, labelled A, B, and C. Four groups of influenza viruses cause human infection: 2 group A (H1N1 and H3N2) and 2 group B. According to WHO, the annual influenza epidemics globally resulting in about 3 to 5 million cases of severe illness, and about 250000 to 500000 deaths

Seasonal flu in Cambodia: Cambodian influenza activity reveals a discrete peak for influenza A during June-December. Influenza A/H3N2 and influenza B were predominant types circulated in 2012 and 2013 respectively, while in 2014 and 2015 A/H3N2 was the predominant subtype circulated. In 2016 Influenza A/H1N1pdm09 and Influenza B were the predominant circulated.

During 2012–2015 the Cambodian sentinel surveillance system for influenza-like illness (ILI) and hospital-based surveillance of acute lower respiratory infection (ALRI) cases, collected a total of 4161 samples. Of these, 1534 (36.9%) tested positive for influenza virus: 17.2% in 2012, 53.9% in 2013, 54.8% in 2014 and 61.9% in 2015. Influenza A virus was detected in 1055 specimens (68.8%) and Influenza B virus was detected in 480 specimens (31.3%).

Avian Flu in Cambodia: Since 2004, there are regular outbreaks of avian influenza A/H5N1 in Cambodia, up-to-now there were 49 poultry outbreaks of A/H5N1 was reported. Fortunately, there were only rare, sporadic human infections related to these outbreaks. The first Human A/H5N1 case in Cambodia was detected in 2005. Since then there were 56 human A/H5N1 cases (37 had died). Between 2012 and 2014, there were 38 human case A/H5N1 (21 cases with severe disease and deaths). Most human infections with avian influenza viruses have occurred after prolonged and close contact with infected birds. Human-to-human transmission with the A/H5N1 virus is exceptional. Since March 2014 up-to now there were no human case infections with avian influenza viruses A/H5N1.

In an effort to monitor for avian influenza infections or the introduction of exotic emerging viruses such as MERS-coronavirus in humans, IPC has screen samples collected from pediatric patients with severe acute respiratory infections (SARI) to monitor for avian influenza infections and MERS-coronavirus infection. In addition, IPC also screened these samples for seasonal influenza strains (A/H1N1pdm09, A/H3N2 and influenza B) to monitor for unusual changes in the circulation of these viruses.

During 2012 and 2015, of the 727 patients (ALRI cases), 89 (12.2%) were positive for influenza A virus: 2.3% in 2012, 16.3% in 2013, 14.9% in 2014 and 5.9% in 2015. Of the 89 influenza A strains detected from ALRI cases 38 (42.7%) were A/H5N1, 40 (44.9%) were A/H1N1pdm09 and 11 (12.4%) were A/H3N2 subtype. No influenza B type was detected among ALRI specimens collected during this period. None of the samples were tested positive for influenza A/H7N9 and MERS-Coronavirus.

Surveillance for avian influenza viruses in poultry and environmental samples in live birds markets in Cambodia conducted in 2011, 2013 and 2015 revealed a high rate of influenza A/H5N1 circulation in this setting and the presence of other subtypes of low pathogenic avian influenza virus such as A/H9N2 virus co-circulating with A/H5N1. The peak avian influenza virus circulation was associated with the Lunar New Year festival. The intervention measures such as market cleaning and closures to reduce risk of human infections and emergence of novel avian influenza viruses should be considered.