Like most of the world, Pakistan has witnessed an increased burden of arboviral infections, primarily from Dengue viruses (DENVs), Chikungunya virus (CHIKV) and Crimean-Congo hemorrhagic fever virus affecting people’s lives. Active circulation of DENV and CHIKV transmitted by mosquitoes has been reported in most parts of the country.
However, the latest incidents of unexplained avian deaths in Islamabad and other cities indicate the presence of the West Nile Virus (WNV) and the potential threat of West Nile Fever outbreak in Pakistan.
West Nile Virus is the leading cause of mosquito-borne disease in most parts of the world. The virus was first isolated in Uganda in 1937, and has since been responsible for thousands of cases of morbidity and mortality in birds, horses, and humans. It is a positive-stranded RNA virus of the family Flaviviridae, which belongs to the same family as the dengue virus. The West Nile Virus is maintained in nature in a cycle between birds and mosquitoes. It is most commonly spread to people by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Although many different species of mosquitoes can maintain this cycle, the Culex mosquitoes play a major role in natural transmission. One concern is that the virus can be passed from mother to baby during pregnancy, delivery or breastfeeding.
After the Covid-19 pandemic, it is important to know how this virus does not spread. The West Nile Virus does not transmit through coughing or sneezing. It does not spread by touching live animals or handling live or dead infected birds. The virus is also not transmitted by eating infected animals, including birds if meat is fully cooked.
Healthcare professionals should remain vigilant about the possible transmission of WNV through blood transfusions. Reporting and testing of dead birds are other ways to detect the presence of WNV in the environment. Citizens may also take reasonability and report dead bird sightings to local authorities.
Cases of WNV infection occur during mosquito season, beginning in the summer and continuing through the fall. There are no vaccines to prevent or medications to treat WNV. Fortunately, most people (8 out of 10) infected with the West Nile Virus do not develop any symptoms. About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea or rash. Most people with febrile illness recover completely, but fatigue and weakness can last for weeks or months. About 1 in 150 people who are infected develop a severe illness that affects the central nervous system, such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord).
There is no specific treatment for West Nile Fever; clinical management is supportive. Physicians should consider West Nile Fever should be considered in any person with febrile or acute neurologic symptoms who has had recent exposure to mosquitoes and blood transfusion, especially during the summer months in areas where virus activity has been reported. At present, most diagnostic laboratories do not have the facility to detect the WNV, which is a serious concern. The government should fill this gap by developing the capacity in existing testing labs and by facilitating private diagnostic labs in establishing the facility.
Currently, no WNV vaccine is licensed for use in humans. In the absence of vaccines, the West Nile Virus infection prevention relies on mosquito control programmes to reduce human-to-mosquito contact. There is no need to panic about this disease or the virus, and people should adopt the same precautionary measures they take to avoid dengue or malaria. Mosquito control is something that anyone from individuals to mosquito control professionals can contribute. The community shall take steps to reduce mosquitoes in and around their homes. Professionals from mosquito control programmes perform tasks to control mosquito larvae and adult mosquitoes and evaluate the effectiveness of the measures taken.
The West Nile Virus infection is a serious threat to public health, especially to the immunocompromised and elderly. Now is the time for the government to add WNV infection to Pakistan’s list of priority diseases. Cases shall be reported to the local health departments using standard case definitions. Arboviral surveillance data should also include West Nile Virus. Besides human disease, data on arboviral infections among presumptive viremic blood donors, veterinary disease cases, mosquitoes, dead birds, and sentinel animals should be maintained. Blood donations, if possible, should also be screened for WNV infection.
Healthcare professionals should remain vigilant about the possible transmission of WNV through blood transfusions. Reporting and testing of dead birds are other ways to detect the presence of WNV in the environment. Citizens may also take reasonability and report dead bird sightings to local authorities. There is an urgent need for the proactive role of relevant authorities and active community participation to prevent any untoward event in the future.
The writer is a Visiting faculty at the Department of Medical Entomology and Vector Control Health Services Academy, Islamabad. He can be reached at uzair@hsa.edu.pk
