17 Types of Most Deadly Infection Causing Viruses

Long before the development of our planet into its present shape, people have faced viruses.

A virus is the smallest form of parasitic micro-organism, typically between 0.02 and 0.3μm, although certain viruses may be as large as 1μm.

Here are 10 worst viruses, based on the probability that a person might die if infected via one of them.

Ebola Virus

Ebola spreads from infected persons and/or animals via contact with blood or other body fluids.

The identified strains vary considerably in reliability. The strains are:

  • Ebola Reston
  • Ebola Bundibugyo
  • Ebola Sudan

The period from virus infection to start of symptoms is between 2 and 21 days. An infected person cannot transmit the disease until symptoms develop.

Marburg Virus

The Marburg virus is similar to the Ebola virus.

The virus can be spilled with the blood, secretions, or bodies, or other body fluid of infected persons.

It can also be spread via contaminated surfaces and materials such as bedding or clothing, through human-to-human transmission.

The period from virus infection to start of symptoms is between 5 to 10 days.

Rabies Virus

Rabies lyssavirus causes rabies in humans and animals.

It normally spreads from an animal’s bite or scrapes. When the symptoms begin, it is normally too late for the patient to be saved. Plus it is fatal without early treatment.

The rabies virus causes two types of Rabies Disease-

  • Encephalitic or Furious Rabies (80% human cases)
  • Dumb or Paralytic Rabies (Dominant or severe case)

HIV Virus

The most deadly virus can be HIV in the modern world. It is an immune system-damaging virus.

The HIV virus gets transmitted via bodily fluids which may be blood, semen, vaginal and rectal fluid, and breast milk.

A person with HIV would most probably develop a serious disorder known as AIDS without medication.

HIV events grow in three stages

  • Stage 1: Acute stage
  • Stage 2: Chronic stage
  • Stage 3: AIDS

It is not possible to cure HIV for now but can be watched closely.

Variola or Smallpox Virus

For thousands of years people fought smallpox. The survivors were left with deep, lifelong scars and, often, blindness.

It was used during the French and Indian Wars as an aerosol bioweapon by giving American Indians smallpox-infected blankets.

The incubation time is between 7 and 17 days for smallpox.

There are two closely linked strains that cause Smallpox:

  • Variola major
  • Variola minor (show less systemic symptoms)


Hantaviruses was found to be a family of viruses mainly spread by rodents like rats, mice etc.

The incubation time for the virus is found to be 1-5 weeks.

Americas hantaviruses are considered to hantaviruses of the ‘New World’ which may cause hantavirus pulmonary syndrome (HPS). The most frequently identified hantaviruses in Europe and Asia, often named “Old Age” hantaviruses, may produce hemorrhagic fever with renal syndrome (HFRS).

Influenza Virus

Flu viruses strongly affect many animals, birds and humans’ respiratory tract.

There are two major influenzas (flu) virus types: type A and type B. Pandemics regarding influenza are characterized by influenza A (recurrence).

The incubation time for the virus is found to be 1-4 days.

Most patients who acquired influenza recover within a week or two, some may experience pneumonia.

Major pandemics in the past century:

  • Spanish flu or Spanish influenza, 1918
  • Asian influenza, 1957
  • Hong Kong influenza, 1968
  • Swine Flu, 2009

Dengue Virus

The dengue virus (DENV) is a mosquito-borne flavirus which leads to the dengue fever. The viruses are linked to West Nile and yellow fever infections.

The incubation time for the virus is found to be 3-15 days.

Aedes mosquito contaminated with DENV spreads dengue fever. It cannot specifically be transferred from person to person.

The dengue virus has four strains:

  • DENV-1
  • DENV-2
  • DENV-3
  • DENV-4


SARS Virus basically causes severe acute breathing syndrome thus SARS. The infection probably originated with bats and then reached nightlife animals named- civets before it finally got humans sick.

There have been seven human coronaviruses discovered so far:

  • HCoV-229E
  • HCoV-OC43
  • HCoV-229E
  • HCoV-OC43
  • SARS-CoV
  • HCoV-NL63
  • HCoV-HKU1


The SARS-CoV-2 was identified in the Chinese town of Wuhan for the first time in December 2019 and is one of the largest families of viruses known as coronaviruses known as SARS-CoV.

The virus originally originated from bats, including SARS-CoV, and traveled across an animal before infecting humans.

The disease that is caused by SARS-CoV-2 is Covid-19. At the moment, no special COVID-19 vaccines or treatments are available.

Rota Virus

Rotavirus is a highly infectious diarrhea virus. In infants and children around the world, it is the most common cause of diarrhea. The virus can be found in a person’s stool before, during, and after diarrhea.

Though kids are rarely killed by virus infection, it is dangerous in areas where rehydrating treatments are not widely available.  Because the virus can survive outside the body for a long time, it is highly contagious.

The virus can contaminate other objects such as toys if the hands of a child are not washed. Other children will then get affected if such contaminated items are also involved.

Japanese Encephalitis Virus

Japanese encephalitis is a flavivirus. This is passed on by the Culex mosquito. The virus can infect pigs, humans, and horses.

The animal may be a carrier of the virus if mosquitoes infect an animal. If other mosquitoes feed these newly acquired animals, they take it and infect other animals. JEV’s natural hosts are likely to be wild birds, and vectors are mosquitoes.

In rural areas the virus is widespread, thus, people are at the highest risk. The chance of surviving the disease varies, but children are at the greatest risk of fatal consequences.

Japanese encephalitis is getting common around towns and cities.

Lassa Virus

Lassa mammarenavirus (LASV) is a kind of arenavirus that leads to the Lassa hemorrhagic fever in primates and humans. It is found to be very similar to the arenavirus of the Old World.

Lassa is usually transmitted to humans via urine or feces of Mastomys rats. Health care staff may be diagnosed with a patient’s Lassa fever directly from urine, stool, blood, or body fluids.

Upon infection, almost every tissue in the human body is attacked by the Lassa mammarenavirus. The outbreak of Lassa fever occurs yearly. Between December and June, the number of people infected peaks.

No approved human Lassa fever vaccines are available yet.

Hepatitis C Virus

The virus of hepatitis C is a virus transmitted by the blood. Viruses can cause acute as well as chronic hepatitis that ranges from a moderate illness of a few weeks to live long one.

Exposure to small quantities of blood is the most popular mode of infection. This could happen by injections use, blood products, unchecked blood transfusion, unsafe healthcare, unsafe injection practices, and sexual activities that allow blood exposure. 

Usually HCV infections are asymptomatic and only a few people get diagnosed in the early stages.  Hepatitis C’s incubation time is between 2 weeks to about 6 months.

HCV prevention depends on reducing the risk of exposure to the virus at health centers and in greater risk populations.

There is no effective vaccine against hepatitis C yet.

Rubeola Virus

Rubeola is a virus that develops the disease measles in the cells that line the lungs and throat. The disease spreads through the air when someone who is infected sneezes or coughs. It is very contagious.

Symptoms like fever, running nose, and cough are produced by people who catch measles. The distinguishing feature of the illness is a telltale rash.

If measles is not treated, complications like the infection of the ear, pneumonia, and encephalitis can occur.

There’s no specific measles medication. Sometimes getting the measles, mumps, and rubella (MMR) vaccine within about three days upon being exposed to the virus can prevent infections.

Yellow Fever Virus

Yellow fever virus is a flavivirus that gets transmitted by the Aedes and Haemogogus mosquitoes to humans. It is related to Japenese encephalitis.

Yellow fever disease is what the virus cases. It usually starts after 3 to 6 days of incubation. The virus is obtained from mosquitoes feeding on infected organisms and can then spread the virus to other humans.

For the first 4 days of the disease, the person is usually viremic until the fever and other symptoms of the disease decrease.

No medication is available to treat or to cure yellow-fever infections. 17D is perhaps the only yellow fever vaccine available today.

Nipah Virus

Nipah virus (NiV) is a zoonotic virus and can be transmitted directly between people through contaminated food and contact. It leads to many diseases, from asymptomatic infections, acute breathing diseases to fatal encephalitis in infected people.

The virus can also lead to serious diseases in animals like pigs which leads to considerable economic losses for farmers. Nipah has caused severe diseases and death to a large number of animals and human beings.

The natural host of the Nipah virus is the fruit bats. It is predicted that the incubation period will be from 4 to 14 days. However, incubation up to 45 days had also been reported.

For either people or animals there is no cure or vaccine available. Taking good care is the primary treatment.

Viruses are many, so are their treatments and cures but the most important point and factor is taking appropriate Precautions Regarding Them.

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