Book review by Prof. N.A. de S. Amaratunga  PhD, DSc

Prof. Nimal Senanayake MD, PhD, DSc, FRCP, eminent neurophysician, creative writer, and film producer continues his major endeavour to educate the public on common diseases and for this purpose he has produced a series of highly readable small books on these topics. Viral diseases that plague our country incessantly have received special attention as most of these deadly infections have no cure and prevention assumes great importance. He has written about all the viral diseases that are endemic in Sri Lanka focusing on what everybody must know about these illnesses. Prof. Senanayake’s crusade against these killers is laudable indeed.

One of those deadly viral diseases is Dengue which is difficult to eradicate and which raises its head from time to time in the underdeveloped tropical countries. Prof. Nimal Senanayake (NS) has brought out a thin volume on Dengue and he has briefly mentioned three other viral conditions, Chikungunya, Zika fever, and Yellow Fever as the causative viruses have a common vector, the Aedes mosquito. NS, as he is wont to do, brings out interesting and captivating stories and anecdotes about the virus, the vector, the history, the clinical picture and outcome so vividly that even those who may not be interested would be glued to the book until the end is reached. The book is well illustrated with labeled colour photos of high quality.

The book begins with a clear introduction to viruses, their classification based on the nucleic acid structure; DNA and RNA. The vector is mainly Aedes aegypti mosquito which is commonly present in the tropics. Story starts with the Aedes mosquito sucking blood from a person who has contracted Dengue via a previous mosquito bite. The virus rapidly spreads throughout the body of the mosquito without causing any harm to it! How nature works for the survival of the virus! And it reaches the salivary glands of the mosquito, another strategic move! Now when this mosquito bites a person free of the infection the virus could enter the blood stream via the saliva of the mosquito and cause the disease. The mosquito survives to carry on its deadly mission. The story is told with the usual story telling ability of the author and takes the form of answers to questions, a technique adopted by NS with excellent designing of questions in their appropriateness enabling the narrative to remain focused.

A detailed description of the journey of the virus in the human body, via the White Cells of the blood stream, and its effects are given in simple language that could easily be understood by the lay person. Yet its scientific quality is not diminished. The virus’ ability to induce the White Cell to produce virus proteins instead of human proteins is explained in clear terms as this character of the virus is vital for its survival and it sets viruses apart from other invasive microorganisms like bacteria. Then the question is asked whether the White Cells keep quiet allowing the virus to do as it likes. No, comes the answer and the response of the White Cells, which are part of the defense mechanism of the body, is described. Some dengue viruses it seems have the ability to derail these mechanisms!

Immune response is explained with the student in mind rather than the lay person and the value of the book to the student as a quick reference is immense. A fascinating battle ensues between the virus and the human immune system. This is of pivotal importance as it will decide the fate of the patient. The author shows his teaching abilities combined with the ability to stimulate curiosity of the reader. The colour photos for illustrations in this section would make it easy to understand even for the lay person. This is an exercise in medical education plus an effort to enhance public awareness of how Dengue becomes deadly compared to other viral infections like common cold which are similar in their manifestation at the beginning.

The clinical features of Dengue are described with the lay person in mind. The ominous signs that indicate the condition may not be harmless are given emphasis. One omission here is the lack of photos to illustrate the signs of the different stages of Dengue, there is only one picture that shows the sub-conjunctival bleeding seen in the eyes in Dengue haemorrhagic stage. The fever pattern which enables the patient as well as the doctor to suspect that the condition may not be a simple viral fever is described in detail with good graphic illustrations. The second stage of the disease is significantly called the decisive stage where the fate of the patient is often decided. In this stage the plasma component of blood leaks through the capillary walls due to disruption of blood clotting mechanism and damage to capillary wall. Plasma leakage is a process in which the protein rich fluid component of the blood leaks from blood vessels into the surrounding tissue. Plasma leakage is the most serious complication that distinguishes Dengue from severe Dengue. The author has described this complication in detail probably for the benefit of students. How patients must take care during the third stage which is the recovery period would be important information to the public. The danger of over hydration via intravenous saline which may cause cerebral oedema is mentioned to caution the doctor as well as the patient.

The description of the structure of the virus which is given next had been delayed probably because there were more important aspects that had to be dealt with at first. However, clinically and pathologically important features in the viral structure are explained adequately. The fact that there are five sero types of the Dengue virus and its significance, ie the ineffectiveness of antibodies formed against one type on the other types is clearly explained. Why a second infection by a different type of Dengue virus could be more dangerous than the first infection, the so called Trojan effect is brilliantly described with reference to the historical incident of the huge wooden horse employed by Greek forces as a ploy to get inside the Troy City fortress. The immune system is tricked by the virus and the defense cells virtually welcome and help the new virus to invade the White Cells just like the Trojan Horse being welcomed into the City of Troy resulting in disaster. One may not find such dramatic explanations in a textbook on Medicine. We must remember that NS is a writer of drama. Front cover of the book carries a picture of a Trojan Horse raising the curiosity of the reader.

The common laboratory tests like blood counts that are usually carried out to diagnose Dengue should be known by the general public. This is very important from the point of view of successful management of the disease. Then the author discuses a very important investigation called NS1 (non-structural protein 1) that could be used from the time the patient develops fever which is not the case with some of the other tests which could only be done after the lapse of a certain period of time after the onset of fever. This test is based on the detection of a protein which is secreted due to the inductive action of the virus but which is not part of the structure of the virus. The book describes all the tests that could be done to confirm the diagnosis of the virus, this information would be very important to the student.

NS, in his usual style, presents the drama of the deadly stages of Dengue. The patho-physiology of the process is discussed with emphasis on the effect of leakage of plasma, how it causes Dengue Haemorrhagic Syndrome and Dengue Shock Syndrome. A knowledge of the clinical features of these complications that help in identifying them would be of value to everybody in countries where Dengue is common. The author very importantly has gone into details of the danger signs that may herald the occurrence of the deadly complications. Author says timely intervention may prevent death.

Prevention of the condition progressing into the deadly stages is the most important measure in the management of the disease. NS employs well designed questions and answers to clearly explain the management of Dengue during this crucial period. NS has not forgotten the patient who could be managed at home. The important measures that should be taken by the caregiver at home are described in great detail. Hydration aimed at prevention of dehydration is emphasised. What type of fluids and what quantities, types of food that should be given and monitoring of passing of urine are described with the layman in mind.

The description of the history of the disease and its spread in the world is thorough and would be extremely useful for the medical historian. Then the author turns his attention to the vector of this deadly disease, the Aedes mosquito. Its origin, the life cycle and its breeding are adequately dealt with. The factors that help the mosquito to survive and spread the virus are mentioned in detail. The prevalence of the mosquito in certain parts of the country is explained and where it prefers to dwell and its meal times are given with good questions and answers. It is the female mosquito that is blood-thirsty; this is a physiological need for the maturation of her eggs. Eggs are laid in stagnant water, a little bit of it is sufficient for her. Another vital bit of information is that these eggs do not die even if the water dries up and could last for six months and then start its life cycle when the next rain comes. These facts would be very important for the lay person who should participate actively to prevent Dengue in his household.

Prof. Nimal Senanayake’s little book is of immense value for the lay person, the medical student, the doctor who battles for the life of Dengue patients, and also for those who are involved in the Dengue prevention campaign. Even a textbook on medicine may not carry all this information in its pages, NS has  covered every aspect of Dengue and therefore the book may interest a wide range of readers.