Strain leads to brain inflammation
Experts studying the West Nile virus in Punjab have seen it show up in three blood donors, raising worries the infection is going undetected in transfusions.
The West Nile virus is a mosquito-borne virus. It has strains from up to nine lineages. Of these, lineages 1, 2, and 5 have been linked to encephalitis or brain inflammation outbreaks in humans. Roughly one in 150 infections leads to encephalitis or brain inflammation.
The Pakistani virus was discovered to be lineage 1, along with other highly pathogenic or disease-causing strains from other regions.
Ten experts, including those from the Wuhan Institute of Virology, Armed Forces Institute of Pathology, University of Agriculture, Faisalabad, captured a total of 4,150 mosquitoes in Punjab during 2016–2017 using carbon dioxide traps. They also studied 1,070 serum samples from humans during the years 2016–2018. The results of their study were published in April in the International Journal of Infectious Diseases.
They found that the Pakistan virus strains were genetically similar to those found in Xinjiang, China and Kerala in India. The virus has already been reported both within Pakistan and in adjacent countries such as Iran, China, and India.
An outbreak in humans was recently documented in Karachi but investigators could not detect it genetically. Although humans catch the virus mostly through mosquito bites they can get it from blood transfusions and organ transplantation.
Three blood donor specimens tested positive for West Nile virus in Punjab but it did not show up in mosquito pools. “This suggests that acute WNV infections may remain undetected and have the potential to be transmitted through blood transfusion,” the experts wrote.
The transmission of WNV like this poses a serious health risk, especially for elderly patients. Recipients and blood banks need to be aware of this possibility. “To the best of our knowledge this is the first report on the circulation of lineage 1 WNV in Pakistan,” they added.
Lineage 1 is responsible for the majority of outbreaks in Australia, India, Europe, and the Middle East.
The study results highlight the need for “urgent, nationwide, coordinated surveillance” to assess the distribution and impact of the West Nile virus in Pakistan.
The experts recommended public health measures to prevent viral transmission including vector monitoring and control, information campaigns to improve personal protection, and district-level deployment of screening tests for blood and tissues.