After Kerala confirmed 63 cases of the Zika virus, Maharashtra has also confirmed its first Zika virus infection. Zika is the latest vector-borne illness to be added to the expanding list of vector-borne diseases that are spreading quickly across continents, creating public health panic.

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Introduction

Given that Zika has now entered India, Indian authorities must immediately summon a worldwide consensus in order to collaborate on evidence-based preventative measures in order to avert the imminent public health disaster that Zika may unleash. Simultaneously, policymakers in developed countries must recognise that the world may be on the verge of a Zika time bomb.

The WHO has stated unequivocally that Zika virus transmission is occurring in India and that the virus is already in circulation in Southeast Asia. As the threat is global in scope, preparedness efforts will need to be on a comparable scale. The developing countries that may become the source of such diseases and spread them must be equipped to avoid becoming hotspots.

A global danger like Zika necessitates widespread preparation, particularly for vulnerable nations like India. This cannot be accomplished without international cooperation. Even so, developing countries such as India continue to grapple with such crises.

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What exactly is the Zika virus?

Zika virus is a flavivirus spread by arthropods and transmitted by mosquitoes. The virus is closely linked to the dengue virus, yellow fever virus, and West Nile virus. Around 20% of patients develop clinical manifestations of Zika virus infection, which include an acute onset of low-grade fever with a maculopapular pruritic rash, arthralgia (particularly in the small joints of the hands and feet), or conjunctivitis (nonpurulent).

Zika virus infection has been linked to neurologic consequences, including congenital microcephaly (along with other developmental abnormalities in infants born to pregnant women who were infected), Guillain-Barré syndrome, myelitis, and meningoencephalitis.

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Epidemiology

Africa, Southeast Asia, the Pacific Islands, the United States of America, and the Caribbean have all seen outbreaks of Zika virus infection. Between 2015 and 2016, the USA, the Caribbean, and the Pacific had a Zika virus epidemic. The Zika virus is called after the Ugandan jungle where it was discovered in 1947 infected a rhesus monkey. Human instances were first identified in 1952 in Uganda and Tanzania. The virus then expanded across tropical Africa and Asia, where occasional cases were reported. The first widely known epidemic occurred in 2007 in Micronesia's Yap Islands, when more than 70% of the population under the age of three was infected, resulting in an estimated 5000 illnesses among a population of 6700.

In 2013-2014, a bigger epidemic occurred in French Polynesia, affecting about two-thirds of the population and resulting in around 32,000 illnesses. Infections with Zika virus were discovered for the first time in the Western hemisphere in February 2014 on Chile's Easter Island.

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Pregnant women's travel warnings

Given the link between Zika virus infection and congenital microcephaly, a number of agencies have recommended pregnant women to avoid or postpone travel to regions below 6500 feet (2000 meters) where Zika virus transmission is ongoing. Regions over 6500 feet (2000 meters) are exempted from travel restrictions since the insects that spread Zika virus are few in these areas and the danger of Zika virus transmission through mosquitoes is low.

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How does it spread?

Humans may acquire the Zika virus in the following ways :

• Bite of an infected mosquito transmission from mother to foetus
• Sexual transmission (including vaginal, anal, and oral sex)
• Transfusion of blood products
• Transplantation of organs
• Exposure in the laboratory

Mosquito bites are the main route of transmission. The Aedes aegypti mosquito, which is found in tropical areas, transmits the Zika virus. However, the Aedes albopictus mosquito, which is found in temperate countries, is also capable of transmitting it. In blood, urine, sperm, saliva, female genital tract secretions, cerebrospinal fluid, amniotic fluid, and breast milk, Zika virus RNA has been identified. Apart from sexual transmission, human-to-human transmission has been reported. The method of transmission is unknown. In the cases cited, intimate contact occurred when the index patient's viral load was very high, and it is conceivable that individuals with Zika virus disease's bodily fluids (such as sweat or tears) are infectious.

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Clinical features

Typically, the incubation time between a mosquito bite and the development of clinical symptoms is between two and fourteen days. Typically, the sickness is minor. The symptoms subside within two to seven days. Following initial infection, immunity to reinfection develops. Severe illness requiring hospitalisation is rare, and fatalities are unusual.

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Symptoms and warning signs

Adults clinical symptoms of Zika virus infection occurs in about 20 to 25% of those who acquire the virus. In one research, females and patients aged 40 years were shown to have a higher frequency of symptomatic infection. However, neither female sex nor age was found to be linked with an increased prevalence of infection.

Zika virus infection is typically characterised by an acute onset of low-grade fever (37.8 to 38.5°C), pruritic rash (erythematous macules and papules may appear on the face, trunk, extremities, palms, and soles), arthralgia (particularly in the small joints of the hands and feet), and non-purulent conjunctivitis. Clinical illness is consistent with Zika virus infection if two or more of these symptoms and signs are present. Additionally, myalgia, headache, dysesthesia, retro-orbital discomfort, and asthenia are often described as clinical symptoms.

Abdominal discomfort, nausea, diarrhoea, and mucous membrane ulcerations are less often seenas symptoms and signs. Thrombocytopenia has been reported and is thought to be mediated by the immune system. Case reports have reported other symptoms such as face puffiness, palatal petechiae, uveitis, temporary hearing impairment, myocarditis, and pericarditis.

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Children 

Infection due to the Zika virus in children may occur intrauterine (vertical transmission during pregnancy), intrapartum (vertical transmission after birth), or postnatally (transmission via mosquito bites). Clinical symptoms of postnatal infection in babies and children are comparable to those seen in adults with Zika virus infection. 

Arthralgia is difficult to detect in babies and young children and may show as irritability, limping, difficulty moving or refusing to move an extremity, palpable pain, or discomfort with active or passive joint movement. There have been no developmental problems reported in normally healthy infants infected with the Zika virus postnatally.

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Complications

Zika virus infection has been linked to congenital microcephaly and foetal loss in pregnant women who are infected, as well as neurologic complications.

Guillain-Barré syndrome- Several cases of Guillain-Barré syndrome (GBS) have been reported in association with Zika virus infection. In general, the chance of contracting GBS is low (from any cause) appears to increase with age. Although GBS is more prevalent in adults and men, it may afflict people of all ages.

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Other neurologic problems

The Zika virus has been linked to a variety of other neurologic disorders, including the following:

• Encephalitis
• Transverse myelitis
• Meningoencephalitis
• Chronic inflammatory demyelinating polyneuropathy
• Brain ischemia
• Encephalomyelitis
• Neuropsychiatric and cognitive symptom

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Diagnosis

Individuals with characteristic clinical symptoms and appropriate epidemiologic exposure should be suspected of Zika virus infection (resident of or travel to an area where mosquito-borne transmission of Zika virus infection has been reported, or unprotected sexual contact with a person who meets these criteria).

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Symptomatic adults

The final diagnosis of Zika virus infection is made by real-time reverse transcription-polymerase chain reaction (rRT-PCR) for Zika virus RNA (in serum, urine, or whole blood) or by Zika virus serology. The main diagnostic specimens are serum and urine; whole blood is an acceptable material for some nucleic acid tests.

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Diagnostic methods

The following is the diagnostic method based on the time of clinical presentation:

1. rRT-PCR of serum (or whole blood) and urine should be performed for individuals who present 7 days after the onset of symptoms to detect Zika virus RNA.
2. Any positive rRT-PCR result confirms a diagnosis of Zika virus infection, and no additional testing is required in these instances. Negative rRT-PCR findings do not rule out the possibility of Zika virus infection and should be followed up with serologic testing (Zika virus IgM and plaque reduction neutralization test [PRNT]).
3. Testing for dengue and chikungunya virus infections should be undertaken as well (unless there is no history of residence in or travel to an area where mosquito-borne transmission of Zika virus infection has been reported, and the only potential epidemiologic exposure is unprotected sexual contact with a person who meets these criteria).
4. Because there is a risk of cross-reactivity with other flaviviruses, all serologic findings should be taken with care (such as dengue virus). Individuals who have been vaccinated against yellow fever or Japanese encephalitis may also show cross-reactivity.
5. Diagnostic testing for Zika virus infection should include Zika virus serologic testing for patients who present >7 days after the start of symptoms (Zika virus IgM and PRNT).

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Management

Infection with the Zika virus has no particular therapy. Rest and symptomatic therapy, such as drinking fluids to avoid dehydration and giving acetaminophen to alleviate fever and discomfort, are the mainstays of treatment.

To minimise the risk of bleeding, aspirin and other nonsteroidal anti-inflammatory medications should be avoided until dengue infection has been ruled out. Because of its link to Reye syndrome, aspirin should not be given to children with an acute viral infection.

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Prevention

1. People who live in mosquito-infested regions should use personal protection as well as environmental control methods to prevent mosquito bites. Aedes mosquitos bite both during the day and at night, and they reproduce in standing water (particularly manmade containers).
2. Personal preventive measures include wearing long sleeves and trousers to avoid mosquito bites, applying insect repellent, and remaining inside as much as possible (with air conditioning, window/door screens, and/or mosquito nets to limit mosquito-human interaction).
3. Individuals who have been infected with the Zika virus may help prevent the virus from spreading to others by taking the same measures to avoid mosquito bites during the first week of sickness (the likely window of viremia).
4. Individuals who have gone to a location where the Zika virus is being transmitted by mosquitos and subsequently return to an area where the virus is not being transmitted by mosquitos should avoid mosquito bites for three weeks following their return (the period during which they could become viremic).
5. Identification and removal of possible mosquito breeding places are among the environmental control methods. Mosquito larvae breed in standing water, therefore people should be told not to allow standing water to accumulate outside (such as in flowerpots, buckets, bottles, jars, and other similar containers near houses). Mosquitoes should not be able to enter domestic water tanks and drains that enable stagnant or standing water. Local and district health authorities can assist with transmission risk reduction.
6. Sexual transmission has been documented. However, the length of virus persistence in sperm and female genital tract secretions may be extended.
7. Men and women with Zika virus infection or exposure (from travel to or residence in mosquito transmission areas, or unprotected sexual contact with someone who has travelled to or resided in mosquito transmission areas) who have a pregnant partner should avoid unprotected sex for the duration of the pregnancy in all areas.
8. Individuals in Zika virus mosquito transmission regions should avoid sexual activity (vaginal, anal, and oral sex) or utilise barrier protection while the active transmission is present.
9. Blood/tissue donation- The Zika virus may be spread via blood and organ or tissue donation.

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Vaccine development

Vaccine research is currently underway. In phase I studies, many inactivated vaccine candidates were shown to produce measurable neutralising antibodies. The vaccine's effectiveness in preventing Zika virus infection in humans will need to be tested in an endemic area with a larger study population.

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Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author is a practising super specialist from New Delhi.