Serological and molecular epidemiology flaviviruses in selected provinces of Zambia

Abstract

Flaviviruses may cause zoonotic or arboviral diseases which are transmitted by arthropods (mosquitoes and ticks). They are capable of spreading by human to human transmission and may result in large outbreaks. In 2010, Zambia was reclassified a low risk zone of yellow fever (YF) by World Health Organization (WHO). To date, none of the YF suspects has been confirmed as a case of YF and the epidemiology of flaviviruses has not been thoroughly investigated in Zambia. Therefore, the objective of this study was to determine the extent to which flaviviruses are causing YF like illness in selected provinces of Zambia. This cross-sectional study was conducted on 93 archived serum samples previously collected from patients presenting in selected health facilities and meeting the case definition of YF suspect from January 2014 to July 2015. Nucleotides from serum were tested by reverse transcriptase polymerase chain reaction (RT-PCR) and nested polymerase chain reaction (nPCR) for flaviviruses and hepatitis viruses respectively. Samples were also tested for YF and dengue fever (DF) antibodies using in-house Immunoglobulin M (IgM) enzyme linked immunosorbent assay (ELISA) and IgM rapid test respectively. Chi-square, two sample test of proportion and logistic regression were the statistical methods used for data analysis. Fourteen percent (13/93) of the serum samples were identified as YF IgM positive. None of the samples tested positive for dengue IgM. All 93 serum samples tested negative for the flaviviruses by RT-PCR or nPCR, whilst 8.6% (8/93) showed acute Hepatitis A and 10 % (2/20) of pooled sera was genetically confirmed for Hepatitis B virus. The median age for the group infected was 9.5 years and the uninfected group was 19 years old with Hepatitis A. Approximately 85 (91.4%) of patients had acute diseases of unknown origin. Viral hepatitis was the cause of morbidity and mortality in acute febrile jaundiced patients as observed in our study areas. Hence, the incidence of acute hepatitis A and hepatitis B was high and need to be considered if flaviviral diseases are suspected.