Killer – Zika Fever : Mosquito–borne virus is potential death sentence


THIS is the season of  fevers. The menace of fevers is rocking the world. True, yellow fever is no longer a global threat, but malaria fever is still with us while  typhoid fever remains on the prowl . Sierra Leone is still at alert for Ebola fever and Saudi Arabia is wary of the Middle East Respiratory Syndrome a.k.a MERS – a viral respiratory illness that is relatively new to humans.

Most people infected with MERS-CoV developed severe acute respiratory illness, including fever, cough, and shortness of breathe. It was first reported three years ago and the Saudi government is “very keen” on finding a vaccine since there is pressing need to control the spread of the MERS virus.

The Lassa fever epidemic,  currently running around in Nigeria,  also comes to mind.

Nigerians are not at ease because there is no  vaccine  against  the disease at  the moment; and  no experimental vaccine has completely protected non-human primates against a lethal challenge.

But right now, the world is not much bothered by MERS, Lassa fever or even Ebola, The world’s latest health scare is a seemingly minor illness that carries a killer wrapped inside – Zika, the mosquito-borne virus that is sweeping across Latin America in the form of a tropical fever, linked to neurological problems and a surge in microcephaly, a condition in which babies are born with abnormally small heads. The defect can cause brain damage and death.

The outbreak of Zika virus has led authorities in some countries to urge couples not to get pregnant, while the US Centers  for Disease Control, CDC, has warned pregnant women to avoid traveling to at least 25 affected countries.

On February 1, 2016, the World Health Organisation (WHO)  declared Zika virus a  public health emergency of international concern. Following an Emergency Committee Meeting  on Zika virus, convened under the International Health Regulations, 18 experts and advisers looked, in particular, at the strong association, in time and place, between infection with the Zika virus and a rise in detected cases of congenital malformations and neurological complications.

The experts agreed that a causal relationship between Zika infection during pregnancy and microcephaly is strongly suspected, though not yet scientifically proven, but all agreed on the urgent need to coordinate international efforts to investigate and understand this relationship better. The experts also considered patterns of recent spread and the broad geographical distribution of mosquito species that can transmit the virus. The lack of vaccines and rapid and reliable diagnostic tests, and the absence of population immunity in newly affected countries were cited as further causes for concern.

After a review of the evidence, the Committee advised that the recent cluster of microcephaly cases and other neurological disorders reported in Brazil, following a similar cluster in French Polynesia in 2014, constituted an “extraordinary event” and a public health threat to other parts of the world.

Director General, WHO, Dr Margaret Chan, in a statement, afterwards,  said: “I am now declaring that the recent cluster of microcephaly cases and other neurological disorders reported in Brazil, following a similar cluster in French Polynesia in 2014, constitutes a Public Health Emergency of International Concern.

Chan said a coordinated international response is needed to improve surveillance, the detection of infections, congenital malformations, and neurological complications, to intensify the control of mosquito populations, and to expedite the development of diagnostic tests and vaccines to protect people at risk, especially during pregnancy.

Although the Committee found no public health justification for restrictions on travel or trade to prevent the spread of Zika virus, it noted that, at present, the most important protective measures are the control of mosquito populations and the prevention of mosquito bites in at-risk individuals, especially pregnant women.


The virus

What’s Zika? This is probably the million-dollar question. Sunday Vanguard  investigations revealed that the  virus was first identified in a  rhesus monkey specie in Africa in 1947. WHO  confirmed  that Zika is actually named after a forest in Uganda where the first infected rhesus monkeys were found. The virus then “jumped”, over time, to humans in Uganda and Tanzania in East Africa.

Hospital information says most of the time, Zika disease infection goes unnoticed. The symptoms are like a mild case of the flu — headache, muscle and joint pain, and mild fever — plus a rash and usually last two to seven days.

Zika is linked to  two serious complications: Neurological problems and birth defects in babies born to infected women. The main neurological complication is  Guillain-Barre syndrome, a disorder in which the immune system attacks the nervous system, causing weakness and sometimes paralysis.

Most patients recover, but the syndrome is sometimes deadly. Cases linked to Zika were first reported in Brazil and French Polynesia.

Microcephaly and other brain deformities in newborns have also been reported, particularly in Brazil.  Since the  Zika outbreak began, last year, microcephaly cases have surged. With no vaccine, or specific treatment, Zika has become a potential death sentence overnight.


‘No more pregnancy’

Recently, the  US Centers for Diseases Control issued a travel ban for pregnant women. Don’t travel to Brazil,  it warned. For women in Brazil,  Colombia, Ecuador, El Salvador,  Jamaica  and at least 18 other Latin America and Caribbean countries, women have been advised to avoid pregnancy for the time being.

An American woman was  reportedly said to have given  birth to a baby with microcephaly after traveling to Brazil.

The Zika virus itself is considered a bit of a dark horse by scientists. A member of the   flaviviridae  family transmitted to humans by Aedes aegypti mosquitoes, it is related to other pathogenic vector borne flaviviruses including Dengue , West-Nile and Japanese encephalitis viruses but prior to the last few months, produced a comparatively mild disease in humans.


The vector

Like dengue fever and chikungunya, two similar diseases, Zika is transmitted by the aedes mosquito species found in tropical and sub-tropical regions. The specific host of the Zika virus is the   aedes aegypti  mosquito. It has a number of aliases including  the yellow fever mosquito, tiger mosquito or stegomyia mosquito.  The vector host is well distributed in Africa, the surrounding tropics and subtropics, south eastern US, the Middle East, South East Asia, Pacific and Indian Islands and Northern Australia.  Sunday Vanguard  gathered that the first documented transmission of Zika virus, outside of its traditional endemic areas in Africa and Asia,was recorded in 2007, when it caused an outbreak on the island of Yap in the Pacific.

Today, Zika virus is considered an emerging infectious disease with the potential to spread to new areas where the aedes mosquito vector is present.

However, there is still no evidence of transmission Zika virus in Europe to date and imported cases are rare.

Entomological information provided by the European Centres for Disease Control and Prevention, ECDCP, shows that the aedes aegypti   is a relatively small insect with an aggressive biting habit. It is easily distinguished by its characteristic black and white pattern due to the presence of white/silver scale patches on a black background on the legs and other parts of the body.

Aedes aegypti  has a high biting and disease risk. It is a known vector of several viruses including yellow fever virus, dengue virus and chikungunya virus. Others are Japanese encephalitis, viral haemorrhagic fevers and Zika virus.

Over the past 25 years there has been an increase in distribution of this mosquito to every continent worldwide making it one of the most widespread mosquito species globally. The success of this invasive species has largely been due to globalisation. It thrives in densely populated areas which lack reliable water supplies, waste management and sanitation.

Historically, this mosquito has moved from continent to continent via ships, and this method of dispersal is thought to present the highest risk. It is even suggested that the mosquito evolved its domestic behaviour in West Africa and its widespread distribution and colonisation in the tropics led to the highly efficient inter-human transmission of viruses such as dengue. Sunday Vanguard  investigations show that  aedes aegypti prefers mammalian hosts and will preferentially feed on humans, even in the presence of alternative hosts. Historically, the mosquitoesi  were found in forested areas, using tree holes as aquatic habitats. But as they have adapted to more urban domestic habitats, they have exploited a wide range of artificial containers such as vases, water tanks and tyres that are often associated with human habitations.

The mosquito has also been found utilising underground aquatic habitats such as septic tanks and adapting to use both indoor and outdoor aquatic habitats in the same area. Adaptation to breeding outdoors may allow for increased population numbers and difficulty in implementation of control methods.

The insect is often not found further than 100m from human habitations. They prefer human habitations that provide resting and host-seeking possibilities and, as a result, will readily enter buildings.


Hope for a vaccine

How far away is a Zika virus vaccine? Experts say research efforts will focus on developing a vaccine for the mosquito-borne illness, but it will take time. However, scientists have quickly turned their attention to trying to develop a vaccine, but a widely available safe and effective Zika vaccine is not likely this year and   probably not in the next few years.

Two potential approaches have been mapped out to developing a Zika vaccine. The first is a DNA-based strategy similar to one employed in a vaccine for West Nile virus, in which a piece of the virus’s genetic structure is inserted into another harmless virus and used to create an immune response in the patient.

The second, more traditional approach would use a live attenuated vaccine in which the virus has been weakened to prompt immunity.

Last week, Genekam, a German biotechnology company, said it had created technology that can not only reveal the presence of Zika pathogens in a blood sample, but also shed light on the quantity in the patient’s blood. The new test can, therefore, definitely determine if a person is a carrier of the Zika virus, as only one in five people infected actually becomes ill, the media reports. Additionally, the test renders diagnostic results in real time, which is relatively quick for a virus of this kind. The test examines DNA and works with chemicals that react to the Zika virus only.

As the race to come up with a vaccine that could fight Zika virus hots up, scientists admit that it’s not going to be easy. Scientists from around the world have pledged to fast-track the research. U.S. National Institutes of Health, Brazil’s Butantan Institute and the Public Health Agency of Canada  have already started their research. Biotech firm, NewLink Genetics and Merck & Co, who are behind the successful Ebola vaccine, are also working on a possible solution. Large Pharmaceutical companies like Sanofi, GlaxoSmithKline and Japan’s Takeda pharmaceutical are also in the race to develop the Zika virus vaccine.

However, despite technological advancements, scientists confessed that there are many challenges to the development of a vaccine.The target profile is women who are pregnant or who are planning to get pregnant – which is about the highest bar there is for safety.

Last  week, Bharat Biotech Ltd., in India, claimed it  already had a possible Zika virus vaccine. It even said  it  actually had two.

It said it could  possibly make one million doses and that  it aimed  to provide help to  fellow BRICS (Brazil, Russia, India, China and South Africa) member-country, Brazil. But the vaccine will also need to undergo further animal trials, which could take some time.

Rage of viruses

In recent years, viruses have been emerging from nowhere. Outbreaks of killer-viruses like SARS, swine flu, and West Nile  have raised international fears. One other virus dominating the headlines is a new strain of bird flu (H7N9) in China. Detected last year, the virus transmits easily from birds to humans, killing about one in five people it infects.

Fears also centre around a novel coronavirus (NCoV), a SARS-like virus. The world’s fears of viruses is clear: Which one has the capacity to become an uncontrollable pandemic. In a world of global air travel, a deadly virus could sweep round the earth with frightening speed.

Viruses outnumber all other life forms on earth. Scientists have estimated that there are about 10 million times the number of stars in the universe.

A virus that kills more quickly than it can spread will die out before infecting a significant proportion of the population. A perpetual fear is that deadly viruses will mutate to develop person to person transmission, allowing rapid spread (rather than, for example, spreading to humans from an infected animal source). The WHO’s recent admission that the novel coronavirus is probably spreading from person to person made the news for this reason.

The creation of genetically modified viruses in the laboratory is believed to be increasing the potential of deadliness of viruses. An altered virus is probably one of the most dangerous viruses you can make. Resaerchers could inadvertently be tampering with the delicate balance of nature and putting the world at risk. No one really knows what the future holds for the battle against viruses. Their resilient nature makes eradication seem unlikely, so man will need to keep innovating.

Killer – Zika Fever : Mosquito–borne virus is potential death sentence