Professor Hugh Pennington: The story so far of the Zika epidemic

Summary: A new year, another epidemic (they’re all “pandemics” in our fearful world) – Zika. In a world of seven billion people linked by rapid transportation, epidemics will become increasingly common. That does not mean that hysteria need accompany each and every one. As with Avian Flue and Ebola, the FM website provides you with reliable information as an antidote to the fear-mongers, starting with this essay by the eminent Professor Hugh Pennington.

A mosquito stops for lunch
An Aedes aegypti mosquito stops for lunch

Zika Virus, the Story So Far

By Hugh Pennington
London Review of Books, 27 January 2016
Posted with his generous permission. Red emphasis added.

On 18 April 1947 in a cage on a tree platform in the Zika Forest in Uganda, rhesus monkey number 766 developed a fever. Its serum was inoculated into the brains of mice. They fell ill. Zika virus had been discovered. The sentinel monkey researchers were the virologist George Dick and the entomologist Alexander Haddow, based at the Rockefeller Foundation Yellow Fever Laboratories in Entebbe. Haddow went on to build a 120-foot steel tower in the forest to study high-flying mosquitoes and their viruses. The best time and place to find Zika virus was in the evening, 80 to 100 feet above the forest floor.

The first human case to be described was in 1964 in another Entebbe virologist, David Simpson; he had a 36-hour fever, some back pain, a headache and a rash. He was better by day three. Antibody studies in Nigeria in the early 1970s found that 40 per cent of people had been infected at some time in the past.

For many years Zika virus resided quietly in the textbooks as a member of the Flavivirus family, a distant and unimportant relative of yellow fever, dengue and West Nile viruses. The books said that it caused only mild symptoms (or none at all), that it was spread by the bite of Aedes mosquitoes, that monkeys were an animal reservoir, and that it occurred in Africa, India and South East Asia.

An alarm bell rang in 2007 when an outbreak occurred on Yap Island in the southwestern Pacific. The infection was mild, with a rash, conjunctivitis and joint pains. But not only was the outbreak the biggest so far recorded – it was estimated that well over half the residents had been infected – the virus had travelled a long way to get to Yap. Perhaps it could spread to the Americas.

Zika Fever

The bell rang again in late 2013 when a large outbreak started in French Polynesia, with the first report of the Guillain-Barré syndrome associated with a number of cases. Guillain-Barré is a neurological illness with paralysis as its main feature.

In May 2015 the first confirmed indigenous cases of Zika virus infection were reported in north-east Brazil. Since then it has spread across the country, and reached Mexico, Haiti, Puerto Rico, Barbados, Paraguay and other South American countries, though not Bolivia, Peru, Chile, Uruguay or Argentina.

But it is the reports of an increase in the number of children born in Brazil in 2015 with abnormally small heads – microcephaly – that have driven Zika to the top of the news. Microcephaly has many causes and is not new. Individuals with it appear on bas-reliefs on Aztec temples. So far, the link between its increase and Zika infections is only coincidence. Evidence demonstrating a definitive link in individual cases will be hard to get. Establishing whether a mother was infected during pregnancy will usually rely on antibody tests; the virus itself does not persist in the body after an acute infection.

The close relationship between dengue virus and Zika makes it virtually impossible to know which virus could have stimulated an immune response. And dengue is currently on the rampage in Brazil. In 2015 there were 1.6 million suspected cases and 839 deaths. The failure of mosquito control is the main reason.

The eradication of Aedes aegypti (the mosquito that transmits both dengue and Zika) in Brazil was driven by the fear of another flavivirus it transmitted, yellow fever. A DDT programme started in 1947. Brazil was declared free of the mosquito in 1958. But in 1976 it came back, probably flying in from Venezuela and the Carribean. Dengue came into the country in 1981. The aim of eradicating Aedes aegypti was dropped and replaced with a control policy in 1986. The mosquito has thrived. It likes people and loves to lay its desiccation-resistant eggs in manmade water containers.

So the relentless spread of dengue after 1981 and Zika in 2015 is no surprise. The possible link between a Zika virus infection and microcephaly is surprising, however. Diseases caused by the other flaviviruses have been intensively studied for many years without microcephaly turning up as a complication. It hasn’t been clearly evident in Zika virus outbreaks elsewhere in the world. But flaviviruses mutate in real time. The classic example is West Nile virus. Isolated at the Rockefeller Yellow Fever labs in Uganda in 1937, like Zika it remained quiet for years. Then in the mid-1990s it got nastier, causing severe brain disease with epidemics in North Africa and Southern Europe. It took off in New York in 1999, and spread rapidly across the continent.

The genomes of the different Zika virus lineages are being sequenced. But developing a vaccine and ensuring that it is safe will take years. The quickest way to stop it in Brazil will be to attack the mosquitoes. The Olympics are near. Perhaps DDT will make a comeback.


Hugh Pennington

About the author

Thomas Hugh Pennington, CBE, FRCPath, FRCP (Edin), FMedSci, FRSE — is emeritus professor of bacteriology at the University of Aberdeen, Scotland. He was chairman of the Pennington Group enquiry into the Scottish Escherichia coli outbreak of 1996 and Chairman of the Public Inquiry into the 2005 Outbreak of E. coli O157 in South Wales.

He frequently writes at the LRB about health care issues.

For More Information

See the pages about Zika at the websites of the WHO and the CDC. Also see “C.D.C. Investigating 14 New Reports of Zika Transmission Through Sex” in the Feb 23 NYT.

Also see “The Emerging Zika Pandemic” by Dr. Daniel R. Lucey (Prof at Georgetown) and Lawrence O. Gostin (Prof of Law, Georgetown) in the Journal of the American Medical Association, 27 January 2016. This line sparked a thousand headlines: “The disease now has “explosive” pandemic potential, with outbreaks in Africa, Southeast Asia, the Pacific Islands, and the Americas.” Time will tell if this is correct or exaggeration.

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3 thoughts on “Professor Hugh Pennington: The story so far of the Zika epidemic”

  1. “Red emphasis added”
    Or, on my reading, not so much – or not at all.

    When it’s put like that, it all seems the the normal progression of a virus though various vectors in a world where nowhere is very far from anywhere else and everything genetic is mutable. Calm, rational and therefore utterly un-newsworthy.

    Of course, in ‘Monsanto World’ where two corporations are responsible for everything that is evil (them and Exxon of course) it’s a different matter, and an opportunity not to be missed.

    In a way though, it’s all summed up by the German reaction to the discovery of residues of Glyphosate in their beer. Yup, infinitesimal quantities of something that has no defined link to cancer (at the levels discovered) in something that contains significant quantities of a known carcinogen.

    There are times when I really wonder how we got as far as we have. Perhaps there’s a god similar to the one in “Gods Song”

  2. I had GB last summer, I was in hospital for 2 months, paralyzed from the waist down, with generalized weakness in my arms and hands. Luckily I never needed to be ventilated, which is an indicator of poor outcomes, as well as being highly unpleasant. I was in high dependency care for about a month, and a regular ward for another one. I had two treatments, IV-IG antibodies ($15000) after which I continued to deteriorate, the second treatment in which I had my plasma swap out to remove the GB antibodies cost about $90000 dollar. Those interventions shortened the duration of the illness by about a month. They also reduced the possibility of lasting effects ( some people never walk unaided again, 7% die, mainly the elderly and people with underlying illnesses). Luckily I have made a full recovery, however I still cant whistle properly..

    The high cost of treatment accompanied by the long occupancy of intensive and high dependency make this illness especially onerous in developing countries. I live in a western European country so my costs were negligible and the care excellent, even so the hospital I was in would have been highly stressed by even 3 or 4 such cases at once. Most rural hospitals would just not be able to cope.

    1. merocaine,

      Thank you for sharing your experience, and best wishes for a full recovery. By “GB” you mean Guillain-Barré syndrome?

      “The high cost of treatment accompanied by the long occupancy of intensive and high dependency make this illness especially onerous in developing countries.”

      Not just in developing countries. Health care crises are the number one cause of bankruptcies in the US. Fortunately you live in Western Europe.

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