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February 22, 2019

How viruses work and how to contain them

Newton hypothesized, if you were walking along a path and were to come across a stone a big stone, pause observe keenly the position of the stone, its’ shape and note what type of stone it was then proceed on along the path to conclude the business that you intended to transact; on your return you were likely to find the stone in the same place, nothing would have changed. Stone is made of non-metallic minerals in nature found in rock layers that form the earth’s outer solid layer. Geologists recognise three types of rock depending on how they are formed, igneous, sedimentary and metamorphic and the scientific study of rocks is called petrology. The word ‘petrified’ so terrified that one is unable to move is derived from the same root. All the types of rocks are formed through physical forces such as very high temperatures and pressure. Sedimentary rock is a little different from the other two in that while it is formed by similar pressure it often contains remains of organisms and other organic materials, which settle in the soils and are then compacted and cemented into rock. So studying sedimentary rock can give clues as to what used to live millions of years ago. Sometimes the fossils, the remains of some animal or plant can be very well preserved in the rock allowing scientists to build an almost complete image of what used to live before. The unfortunate thing for science is that to date no one has been able to put together everything needed to bring the creatures back to life. That might sound like a nightmare movie scenario, but medicine already faces such scenarios everyday. They are called viruses.

A virus is a tiny infective agent that cannot be seen even with a light microscope. Viruses range in size from 25 to 500 nanometres in diameter. One nanometre is one-billionth of a meter. To put that in some context the typical human being is about a million times bigger than the average bacteria and ten million times larger than the a virus. If a virus were enlarged to the size of five shilling coin, then a bacterium would be the size of a dinner plate and a human being would stretch in height and diameter a distance from Nairobi to almost Eldoret. The typical virus is made up of genetic code wrapped up in a protein coat. On its own it cannot grow or reproduce and therefore unless it is a living organism is neither alive nor dead. There are about 100 recognized families of virus. The viruses are grouped together according to their shape, they can look like rods, or filaments or round; their behaviour and whether they contain RNA or DNA, the basic blueprint for cells to replicate. Examples from the DNA families include herpes and chickenpox while RNA viruses include the common cold, HIV, hepatitis, measles, polio and Ebola. Ebola belongs to a group of five families; Arenaviridae, Bunyaviridae, Filoviridae, Flaviviridae, and Paramyxoviridae. These viruses all cause haemorrhagic fever, which are infectious diseases that interfere with the blood's ability to clot. The initial symptoms are like malaria and the incubation period is about the same about ten days, the difference is that the patient eventually begins to bleed from under the skin, the mouth, eyes and ears and internal organs as well.

People get infected by coming into contact with infected body fluids. Because the human being is not the natural host of the virus their survival depends on an insect or animal host, in the case of Ebola the fruit bat is the host. It is believed that people become infected when they pick fruit that the fruit bat has licked or bitten, depositing saliva on the fruit, which the person then takes in. But not everyone dies from exposure to the virus, there are some people who rather than succumbing to the virulent disease that is of serious concern to the world today, they develop a mild form of the disease and then develop immunity. In a study in Gabon where more than 4,000 blood samples were taken it was found that about 15 per cent of the population has antibodies to the virus and were therefore immune from the disease. They had not reported the dramatic symptoms that characterise the disease. This gives hope that a vaccine can be found.

But until a vaccine is found, and this would be one for just one specific virus public health measures remain the best way to assure the health of everyone. Simple measures like hand washing are effective in preventing disease from spreading and wash away parasites, bacteria and viruses that cause disease. That requires clean running water for everyone. Four out of ten persons in Kenya lack safe water supplies and two-thirds do not have proper sanitation. These are the people vulnerable to any disease outbreak. Like any virus, Ebola will test the public health system and then we descend back into the usual torpor, but the message should be that inertia should not be the natural state of being.

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