Zika virus - a worldwide threat to public health
World Health Organization (WHO) has declared Zika virus to be public health emergency of international concern. It announced the declaration in early February 2016. This implies that the situation is serious, sudden, unusual or unexpected and the disease caused by Zika virus is likely to spread beyond the borders of the affected countries.
Zika virus is a mosquito-borne single-stranded RNA virus related to dengue virus. In the Americas, Zika virus is primarily transmitted by Aedes aegypti, but Aedes albopictus mosquitoes can also transmit the virus.
Areas where Zika virus has been found –
The reliable sources present the following facts regarding the incidence of occurrence of Zika -
- Prior to 2015, Zika virus outbreaks have occurred in areas of Africa, Southeast Asia, and the Pacific Islands.
- In May 2015, the Pan American Health Organization (PAHO) issued an alert regarding the first confirmed Zika virus infections in Brazil.
- Currently, outbreaks are occurring in many countries.
- Zika virus will continue to spread and it will be difficult to determine how the virus will spread over time.
Transmission of Zika virus –
Through mosquitoe bites -
It is spread to people primarily through the bite of an infected Aedes species of mosquitoes – A. aegypti and A. albopictus. These are the same mosquitoes that spread dengue and chikungunya viruses. These mosquitoes have the following characteristics that facilitate the transmission of Zika virus:
- Mosquitoes that spread chikungunya, dengue, and Zika are aggressive daytime biters. They can also bite at night.
- These mosquitoes typically lay eggs in and near standing water in things like buckets, bowls, animal dishes, flower pots and vases. They prefer to bite people, and live indoors and outdoors near people.
- Mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites.
From mother to child –
A mother already infected with Zika virus near the time of delivery can pass on the virus to her newborn around the time of birth, but this is rare. It is possible that Zika virus could be passed from a mother to her baby during pregnancy. Still studies are under way as to how it is spread during pregnancy. To date, there are no reports of infants getting Zika virus through breastfeeding. Because of the benefits of breastfeeding, mothers are encouraged to breastfeed even in areas where Zika virus is found.
Through infected blood or sexual contact –
Spread of the virus through blood transfusion and sexual contact has been reported.
Symptoms of Zika virus disease –
About 1 in 5 persons become ill when infected with Zika virus. The incubation period that is the time from exposure to symptoms for Zika virus disease is not known, but is likely to be a few days to a week. The illness is usually mild with symptoms lasting for several days to a week. The following are the most common symptoms of Zika virus disease:
- Fever and headache
- Joint pain
- Muscle pain
- Conjunctivitis (red eyes)
People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. Zika virus usually remains in the blood of an infected person for about a week but it can be found longer in some people.
A diagnosis of Zika is made by performing specialized blood tests to look for the presence of Zika virus in the blood during the first week of infection.
As there is no specific medicine to treat Zika infection, treatment is symptomatic, that is, drugs are given to manage the symptoms of the disease. Treatment involves the following:
- Get plenty of rest.
- Drink fluids to prevent dehydration.
- Take medicine such as acetaminophen or paracetamol to relieve fever and pain.
- Do not take aspirin and other non-steroidal anti-inflammatory drugs.
- If you are taking medicine for another medical condition, talk to your healthcare provider before taking additional medication.
Prevention from mosquito bite - As there is no vaccine for prevention of Zika virus disease, the most effective measure is the prevention of mosquito bites. Prevent the mosquito bite for the first week because Zika virus is present in the blood. If a mosquito bites in this period, it is most likely to get infected. An infected mosquito can then spread the virus to other people. Prevention of mosquito bites involves the following measures:
- Wear long-sleeved shirts and long pants.
- Stay in places with air conditioning or that use window and door screens to keep mosquitoes outside.
- Sleep under a mosquito bed net if you are overseas or outside and are not able to protect yourself from mosquito bites.
- Use insect repellents, following product label instructions. Do not apply insect repellent creams on babies younger than 2 months of age. Cover crib, stroller, and baby carrier with mosquito netting.
- Do not apply insect repellent creams onto a child’s eyes, mouth, and cut or irritated skin.
Prevention from sexual transmission - There is evidence that Zika virus can be sexually transmitted from man to his sex partners. Men, who have lived in or traveled to an area with Zika virus, should abstain from sex or use condoms the right way every time they have sex. If the partner is pregnant, they should abstain from sex or use condom the right way for the duration of the pregnancy. It is not yet clear how long the Zika virus will be present in the semen. One report found the virus in semen at least two weeks after illness. But it is not definite how long the Zika virus can be sexually transmitted from a male partner. Since Zika virus can remain in semen longer than blood, someone might have a negative blood test but a positive semen test.
Prevention from infected blood – Every precaution must be observed that blood contaminated with Zika virus is not transfused to people requiring blood transfusion. Blood banks must ensure by proper testing of blood for Zika virus that their blood is free from any contamination with the virus. Though many countries at present don’t have facilities of testing for Zika virus, sooner or later they will have to evolve such facilities because of its potential threat of global dimensions.
Zika virus infection and congenital microcephaly –
There have been reports of congenital microcephaly in babies of mothers who were infected with Zika virus when pregnant. Zika virus infections have been confirmed in several infants with microcephaly. But studies are under way to investigate the association of Zika virus infection and microcephaly, including the role of other contributory factors. If the brain in microcephalic babies is really very small, it is more likely that the child will have more serious disability throughout life, whereas if brain is moderately small, the child will likely have less disability. There is, in fact, no cure for microcephaly. Children with microcephaly have significant developmental delays and cognitive impairment, which is quite overwhelming to the families.
Recently, a team of researchers working with lab-grown human stem cells suspect they have discovered how the Zika virus probably causes microcephaly in fetuses. The virus selectively infects cells that form the brain's cortex, or outer layer, making them more likely to die and less likely to divide normally and make new brain cells.
The bottom line –
Zika virus continues to dominate news headlines all over the world with warnings that it is likely to spread into the Americas. This has created a state of confusion in minds of many. But we should not forget that its transmission to the Americas or any other country can be checked if people are well aware of the facts about the Zika virus so that they can take effective preventative measure. Apart from government measures adopted by various countries, campaigns for individual awareness about the disease will play a significant role in arresting its spread.