The World Health Organization’s statement of advice to visitors to Rio for the Olympic Games which included the phrase, ‘Avoid visiting impoverished or overcrowded areas’, ruffled a few Rio feathers. Some Brazilians feel that such statements unfairly stigmatize poor residents. The truth is that the spread of the Zika virus has turned ‘explosive’ in many parts of the world irrespective of their GDP, dealing a blow to developed health care systems of countries such as the US. According to WHO, as of June 15, 60 countries and territories report continuing mosquito-borne transmission of Zika.
Closer to home, strict measures have been implemented at the airport to screen individuals from or are returning from Zika prevalent countries in Latin America and Africa such as Brazil, Venezuela, Columbia, Mexico and the Caribbean. The Zika virus is contracted either through mosquito bite or sexual contact. Because the main vectors of the Zika virus Aedes aegyptii and Aedes albopictus, are prevalent across Sri Lanka due to favourable climatic conditions, exacerbated by the recent floods, Sri Lanka is a prime target for the virus. Stagnant pools are ideal breeding ground for these vectors. The transmission of the virus depends on the prevalence of the vectors carrying the virus.
“In fact except for areas like Nuwara Eliya, where the extreme cold weather prevents the vector from spreading, Aedes aegyptii and Aedes albopictus are widespread. This is the virus’s primary mode of transmission,” said Medical Research Institute (MRI), Consultant Medical Virologist, Dr. Janaki Abeynayake. A special Zika diagnosis unit has been set up at Borella Medical Research Institute, the only such facility in the country. “We have screened people who’ve had pure exposure to destinations such as Venezuela and Mexico,” said Abeynayake. Although some have exhibited similar symptoms the tests have turned out negative.
Zika virus triggers symptoms similar to dengue, such as fever, skin rashes, myalgia (muscle pain), non purulent conjunctivitis (redness of the eyes) and joint pain. This can be a major obstacle for mitigation, often leading to misdiagnosis. Therefore it is advised that any person displaying dengue symptoms be hospitalized.
“But 20 per cent of Zika infected people are asymptomatic,” said Abeynayake. Which means that their immunity is strong enough to suppress any symptoms triggered by the virus. “During screening we look for clinical symptoms. However, according to research, viral loads are low in asymptomatic people and since immunity of such people is considerably high the chances of passing the virus to others is negligibly low.”
“Investigations and research based on Zika transmission in prevalent countries indicate that pregnant women are especially at risk,” said Dr. Abeynayake. Although Zika is termed as a mild disease, pregnant women are at risk as they could give birth to babies suffering from microcephaly, characterized by abnormally small heads that retard brain development. Women can give birth to microcephalic babies if they are exposed to viruses such as rubella or herpes simplex during pregnancy. “But viruses like Rubella affect during the first trimester of the pregnancy, as opposed to Zika that can affect the foetus at any stage in pregnancy. Consequently, expectant women are strictly advised against flying to Zika prevalent countries.
Apart from microcephaly, Zika can lead to Guillain-Barré syndrome (GBS), an adult neurological disease that affects the nervous system, forcing one’s own immune system to damages nerve cells, causing muscle weakness, and sometimes paralysis.
Dr. Abeynayake explained that studies based on non vector mode transmission of the Zika virus in prevalent countries, indicate that Zika can be contracted through sexual, intrauterine, perinatal, saliva and blood transfusion associated transmission. The Zika virus can be transmitted through the exchange of vaginal and seminal fluids during sexual contact. Consequently, it is advised that those who have visited Zika prevalent countries abstain from engaging in sexual activity for up to 12 days, the incubation period of the Zika virus.
The Zika virus is not necessarily fatal, although it’s a debilitating disease, said Abeynayake. “However, since the two vectors, the primary mode of transmission, are widespread in Sri Lanka it could reach epidemic levels if the virus gets into the country. To prevent such a scenario we must strengthen airport screening,” opined Abeynayake. She further advised against pregnant women from visiting Zika prevalent countries, sexual exposure while in such countries and advised the use of mosquito repellent and bed netting.