The Zika Invasion - Causes, Symptoms, Diagnosis, Treatment and Prevention

The Zika virus has recently come into prominence and is causing alarm in concerned circle.  The virus is spreading rapidly - it is spreading so fast that it is expected to  infect nearly four million people in the Americas in the next 12 months.

The World Health Organisation is set to convene an international health regulations emergency committee on Zika virus on February 1 in Geneva to ascertain whether the outbreak constitutes a public health emergency of international concern.

World Health Organization Director-General Margaret Chan said, "The level of alarm is extremely high," which is why they are considering declaring a public emergency.

Map showing spread of the Zika virus

Why is the spread of the Zika virus being taken so seriously? What disease does it cause?

The chief apprehension with the Zika virus is that it  has been associated with neurological problems in babies born to mothers infected with the virus during pregnancy.

The virus can pass through the placenta and amniotic fluid in infected pregnant women  and may trigger brain damage with failure in development of the brain. Because the brain does not grow at a normal pace, the skull doesn’t, either.  This causes the brain as well as the skull  to be smaller  in size – this abnormality is known as  microcephaly (abnormally small head) in new-born babies. This is a serious condition which can cause severe  abnormalities in babies.

The affected babies may have mental retardation, delayed motor and speech functions, seizures, facial distortions, dwarfism, hyperactivity and spasticity and a difficulty in balance and coordination of the body.

Women who are infected in the first trimester is believed to be at an increased risk for having a child with microcephaly. Scientists do not yet have sufficient knowledge of effects of the infection  in the second and third trimester.

The link between Zika infection and microcephaly has not been conclusively proved but the association is strong enough to cause health officials to caution pregnant women to avoid travelling to countries at risk of Zika virus transmission. Women in high risk areas have also been advised not to get pregnant for at least 2 years.

Microcephaly

  Another important condition suspected to be caused by the virus is the Guillain-Barré syndrome (GBS). This is an autoimmune condition in adults in  which the immune system attacks the nervous system, sometimes leading to paralysis. A direct causal relationship has not been established between Zika infection and GBS, but  the incidence of GBS has been seen to be significantly higher in areas where  Zika infection is common.

The main symptoms of GBS are muscle weakness, tingling  and numbness of the body which starts at the fingers and toes, difficulty in walking steadily, low back pain and difficulty in moving the eyes or face, talking chewing and swallowing. The condition may spread rapidly throughout the body with muscle weakness leading to paralysis. If the  respiratory muscles  are affected  by GBS, it  is an acute emergency  and may lead to death.

Spread of the Zika virus

The virus is spread by bites from an infected Aedes mosquito, especially  A. aegypti. The Aedes mosquito is a daytime mosquito, characterized by whitish bands on its legs and  markings on its body.  It is more common in urban areas and breeds in stagnant water in containers  in and around the house.

The Aedes Mosquito

 The female mosquito needs human blood to get nutrients for the developing eggs and transmits the virus through its saliva at the time of biting.

The Aedes mosquito also transmits other diseases like malaria,  dengue and chikungunya.

Incubation period

 The first symptoms  begin 2-7 days after the bite of an infected mosquito. The Zika virus passes very quickly through the bloodstream and in most cases, the virus would clear from the bloodstream within about a week.

Symptoms of  Zika

-Mild and only one in five humans bitten by the mosquito will develop the disease. Most people may be unaware that they are infected. Those people then become carriers during the time they have symptoms.

- Common symptoms are fever, headache, rash and possible pink eye (conjunctivitis). Other symptoms are muscle pain and headache. A feeling of general ill health may persist for weeks.

-  Symptoms may last for several days to a week.

- Complications or death is rare.

Diagnosis of Zika

In most cases, diagnosis of Zika is based on the clinical symptoms  and the outbreak of the disease in the locality.

 Virological (PCR) tests may be positive in the first 3-5 days of infection when the virus is in the blood. Serological tests which detect the presence of antibodies to the virus are useful only after 5 days of the infection when the antibody levels become detectable in the blood.

No commercial tests are available to diagnose Zika but blood tests can be done at state laboratories

Treatment of Zika infection

- There is no specific medicine for Zika. Treatment is symptomatic to relieve the symptoms and support the patient through the  infective phase.

- Medicines like acetaminophen or paracetamol should be taken to decrease muscle pain and fever. NSAIDS like Ibuprofen and Naproxen should be avoided since they increase the risk of bleeding from the mucus membrane.

- Adequate fluids should be taken to avoid dehydration.

- Rest is necessary since the viral infection may cause fatigue .

- Contraceptives should be used  to avoid getting pregnant when there is a known case of Zika in the locality.

- No vaccines are presently available to prevent Zika although may become available in about 3 years..

Prevention of Zika Infection

Zika can be prevented by (a)  not allowing mosquitoes to breed (b) avoiding mosquito bites.

(a) Preventing breeding of mosquitoes

- Outdoor containers in which water  can collect(flower pots, bottles etc) should be emptied out and removed.

 - Accumulated garbage, including piles of leaves or that around waste bins  should be cleaned. Restaurants and other eateries in the locality should be checked  for proper garbage disposal.

- Water tanks in the house or outdoor ponds  should be covered to prevent mosquitoes from getting in and laying eggs.

- Screens and mosquitoes nets should be attached to doors and windows to prevent mosquitoes from entering the house.

- Drains and pipes which can accumulate water should be cleaned out and covered.

(b) Avoiding mosquito bites.

- Long sleeved shirts and blouses at should be worn at all times and more specially during the day since the mosquito bites mainly during the day.

- Mosquito repellants  should used at all times.

 - Sleeping under mosquito nets  should be encouraged.

Conditions which have symptoms similar to Zika

Dengue

Chikungunya

Yellow fever

Malaria

Leptospirosis

Rickettsia

Measles

The Zika virus was first isolated in 1947 from a rhesus macaque monkey from the Zika forest in Uganda (hence the name). Since it was localized  in that area and the symptoms it produces were mild and considered relatively harmless, it  did not receive much attention by health authorities. But the recent rapid spread and as knowledge about its connections with microcephaly and  the Guillain-Barré syndrome has come into focus, it is being viewed with more concern.