Viruses are an organism that is at the edge of life itself. It’s hard to say if they are living or non living. Some of them can be dead for hundreds of years before entering a host and becoming alive. There are more than 5000 virus species known to man. Some of these have been eradicated by science while others keep evolving into new strains that are harder to fight. And for some we just have no known cure. Here we go with top 10 deadliest viruses known to science.
Dengue is a virus that has just been discovered a few years ago. It is fast becoming an epidemic in over 100 countries. It has characteristics similar to malaria. It spreads through female Aedes mosquito bites and results in a fever that can last from 2 to 7 days. Dengue fever causes flu like symptoms of high fever, headaches, muscle and joint pain and a rash. There is no vaccine as of yet but there are a few potentials under development.
9. Yellow Fever:
Yellow fever has been around for many centuries. There have been major outbreaks of yellow fever in history including during the Haitian revolution of 1802 which killed half of the French army. The virus is transmitted through mosquito bites and travels through the lymphatic system after incubating for a period of 3 to 5 days. It starts attacking the organs such as kidneys, heart, adrenal glands and liver. There is no known cure but there is a vaccine that inoculates for a period of 10 years.
Rabies virus is transmitted from animals such as dogs, bats, monkeys and foxes. This virus has been eliminated in a few countries but is present in most. It has a varying incubation period that depends on where the patient was bitten. Once the virus reaches the central nervous system it travels to the brain. The initial symptoms are mild such as fever and headache but once the virus kicks in it leads to acute pain, violent movements, depression, uncontrollable excitement and an inability to swallow water. Later it causes mania, coma and finally death. There is a vaccine available for both humans and animals.
Hantavirus is transmitted through rodents and can be transmitted without any direct contact with one. The virus can travel through aerosols of rodent excrement, urine or saliva. Exposure to dust particles encrusted with rodent excrement can lead to infection. It can cause hemorrhagic fever with renal syndrome (HFRS) or hantavirus pulmonary syndrome (HPS). The symptoms are flu like initially and then include extreme albuminuria, ecchymosis, scleral injection and bloodshot eyes. HFRS can be treated with ribavirin but there is no cure fore HPS.
Measles virus has been crusading against humans for many centuries. It has destroyed armies and reduced entire population of countries to a fraction. It spreads through direct contact with the infected patient and through aerosol droplets and respiratory secretions. After the incubation period of 14 days the patient suffers cold like symptoms such as runny nose, fever, cough and conjunctivitis. Later inside of the cheeks break into white spots and the whole body is covered with red blotches. Measles is not life threatening unless accompanied with other complications. There are medicines to manage the disease and vaccinations given to children.
5. Hepatitis C:
Hepatitis C is a dangerous virus as there are no symptoms of infection and patients sometime don’t find out that they are infected for many years till their liver starts failing due to the virus. The virus is transmitted through contact with blood of an infected person. It can spread through sharing drug needles, tattoos, piercing, blood transfusions, organ transplant or dental exposure. It can also be transferred sexually. There is no vaccine against hepatitis C as of yet.
Influenza has been around for many centuries. There are pandemic outbreaks about 3 times every century. It is an air borne virus that spreads between birds and mammals through cough and sneezes. It can also spread through blood, bird droppings, saliva and nasal secretions. Symptoms of flu appear in a couple of days and cause runny nose, fever, head and body aches, irritated eyes and fatigue. There are vaccines against flu but they need to be kept updated as the new strains of flu virus keep evolving every year.
3. Hepatitis B:
Hepatitis B is a dangerous virus that is transmitted through exposure to infected blood. It can spread through sexual activity, infected needles, and from mother to child during pregnancy. The symptoms include yellowing of skin and urine, vomiting, nausea, fatigue and abdominal pain. There is no known treatment but most adults can survive an attack and develop a natural immunity. Some patients may face liver failure or liver cancer.
Rotavirus causes diarrhea in children and almost everyone on earth is affected by this virus in their childhood at least once. With each infection the immunity builds up but what makes this virus deadly is that in many countries adequate medical facilities aren’t available and millions of children die each year due to rotavirus infection. The infection occurs when contaminated stool is ingested. Water or food contaminated with dried stool remains can also cause infection. The symptoms are watery diarrhea, vomiting, high fever, dehydration, loss of appetite and mucus in stools. If dehydration is not fought with continuous liquid replacement it can lead to death.
The most dangerous virus has to be the Human Immunodeficiency Virus or HIV. It has killed more than 25 million humans since 1981. It spreads mainly through sexual intercourse, exchanging needles, breast feeding or vertical transmission from mother to child. It can pass through any of the human fluids including blood, semen, saliva, tears, milk and vaginal fluid. When a person gets infected the virus takes over the immune system and kills CD4+ T cells that fight infections. The symptoms are sudden weight loss and recurring infections of skin and respiratory system. There are no vaccines or cures available.