The 9 Most Lethal Virus Diseases in the World

On December 2019, a new viral disease, COVID-19, caused by a new strain of coronavirus, SARS-COV-2, was identified in Wuhan City, Hubei Province, China. In the mid-2020, the disease had virtually spread to all countries of the world.

According to the latest figure (February 19, 2022), more than 422 million people have been infected by the virus resulting to more than 5.9 million deaths.

The eruption of this viral disease and the aftermath of its spread offers a grey glimpse of the susceptibility of humans to future new outbreaks of viral diseases.

In relation to COVID-19, a viral infection, this article will look at the 9 most deadliest virus diseases which posed as a threat to and/or are a threat to human's existence since 2000.

In spite of the existence of rabies vaccination (both for pets and humans), the disease kills more than 50,000 people yearly. The most affected are Asian and African countries which account for 95% of the total annual deaths. Children under the age of 15 form the largest percentage of the infected, and who highly succumb to the disease.

Rabies virus which causes rabies is spread through saliva when an infected animal bites another animal or human. In rare cases, a person can become infected with rabies when a rabies infected animal licks an open wound or the person's mucus membranes such as eyes and ears.

Rabies is almost always fatal when a person infected by rabies virus begins showing the symptoms of the disease. If immediate treatment is not sought to manage the symptoms, the person is most likely to succumb to the disease.

According to Mayo Clinic, any mammal can transmit the rabies virus to people including cats, goats, horses, foxes, monkeys and coyotes.

WHO states that 99% of rabies virus transmission to humans results from dogs' bites.

Marburg virus disease is caused by Marburg virus that was detected in 1967 when two outbreaks of the disease occured in Marburg and Frankfurt (Germany), and Belgrade (Serbia).

The mortality rate of the disease is 88% making it one of the most deadly viral infections in the world.

Rousettus bats are the natural hosts of Marburg virus.

The disease is spread via direct contact with bodily fluids or tissues of an infected person or touching a surface that's been contaminated by the virus. Prolonged exposure to mines and caves can lead one to catching the disease.

Many of the Marburg patients develop severe complications between 5-7 days after being infected by the virus.

In severe cases, a person will die from the infection 8-9 days after showing the clinical symptoms of the disease.

There is no cure, vaccine or specific treatment for the disease.

Measles, one of the world's most contagious diseases, is spread through respiratory droplets and touching contaminated surfaces.

The disease is termed as a childhood disease due to the sheer number of the infected, and dying from the disease, being children. The disease is mostly fatal among children especially the under nourished.

Despite the availability of measles vaccine, more than 100,000 people die annually from the disease especially children under the age of 5. In 2018, more than 140,000 people died from the viral infection.

There is no cure or specific treatment for the disease.

Ebola virus disease is caused by Ebola virus. The various strains of Ebola virus were detected in different years and regions. Zaire ebolavirus is the deadliest strain of Ebola virus. It has fatality rate of up to 90%. The average case fatality rate of EVD is 50%. Depending on the strain of Ebola virus, the case fatality rate ranges between 25% to 90%.

Ebola virus disease was initially discovered in 1976 when two outbreaks of the disease occurred in Nzara (South Sudan) and Yambuku (Democratic Republic of Congo).

The 2014-2016 EVD outbreak marked the largest outbreak of the disease since its discovery in 1976. The outbreak began in Guinea spreading to neighbouring countries, Sierra Leone and Liberia. About 28,616 people in the three regions were infected resulting to an approximated 11,310 deaths.

While the disease spread to some African and European countries including USA, the impact was minimal.

The disease is spread through direct contact with bodily fluids and organs of infected people, and touching surfaces contaminated by the virus.

The origin of the virus is not yet known though scientists speculate fruit bats or nonhuman primates such as chimpanzees and apes are possible animal source of the virus.

As is the case with MVD, Ebola is fatal if the infected person is not treated early on.

There is no cure or specific treatment for the disease.

Unlike MVD, a vaccine for Ebola was developed which proved highly protective against the disease in a major trial that was exercised in Guinea in 2005.

This is perhaps the most deadliest virus disease since its discovery in the early 1980s. The disease still infects and kills many people annually even though there are specific treatments that can enable the infected to live a healthy-long life.

According to WHO, an estimated 75 million people have been infected with the HIV virus and about 32 million have died of HIV since the first outbreak of the disease in the 1980s.

The origin of HIV virus is not known. Scientists suspect people were initially infected by siman immunodeficiency virus (SIV) found in chimpanzees when they consumed meat of infected chimpanzees. Once the virus circulated in human population, it mutated into HIV which only causes illness in humans.

HIV is spread through direct contact with bodily fluids of an infected person e.g. through sexual intercourse, breastfeeding and blood donation.

AIDS is the advanced stage of HIV. At this stage, the body's immune system is too weak to fight opportunistic diseases taking advantage of its weakly state. "Untreated HIV can progress to AIDS within a decade," states WHO. "There is no cure for AIDS, and without treatment, life expectancy after diagnosis is about three years. This may be shorter if the person develops a severe opportunistic illness. However, treatment with antiretroviral drugs can prevent AIDS from developing."

A contagious respiratory illness, flu can cause mild to severe illness, and in some cases it can lead to death.

Flu is caused by flu viruses that usually infect nose and throat. In some instances, they can infect the lungs.

Flu is different from cold and it usually comes suddenly unlike cold.

It is not yet known fully how flu viruses are transmitted from person-to-person. Scientists believe the viruses are spread through air by means of respiratory droplets that are discharged by infected people when they talk, cough or sneeze. In rare circumstances, a person can get the disease by touching surfaces that have been contaminated by the virus.

It's recommended that people get vaccinated each year to prevent them from getting the disease. In addition, flu antiviral drugs are available in treating the illness.

According to WHO, an estimated 250,000-500,000 people die annually from the disease.

MERS is caused by a strain of coronavirus known as Middle East respiratory syndrome (MERS-COV). The virus was identified in Saudi Arabia in April 2012.

It is not known where MERS-COV originated from but scientists believe an animal source was responsible for the outbreak. The virus has been found in a bat and camels. It is thought an infected bat transmitted the virus to camels. When humans came into contact with infected camels' meat or milk, they became infected.

"Close contact between a person and an infected camel appears to be necessary for the transmission of MERS-COV. It has been suggested that the virus could infect humans through air, and through consumption of raw camel milk or uncooked camel meat," states Medical News Today.

At the end of 2019, an estimated 2,494 cases of the infection and 858 associated deaths were reported worldwide. The case fatality rate of the disease worldwide was 34.4%.

SARS is caused by severe acute a in eirespiratory syndrome (SARS-COV). The virus was identified in 2003 in China.

The initial animal source of the virus is not known though scientists suspect bats are the natural reservoir of the virus.

It is thought the virus began in bats then spread to civet cats. Humans became infected through direct contact with the infected civet cats. The first recorded human infection occurred on November 2002 in Guangdong Province in southern China.

Human-to-human transmission occurs when an uninfected person inhales liquid droplets that have been discharged into air by an infected person through coughing, sneezing or talking. Also, a person can get the virus by touching surfaces contaminated with the virus.

The disease which had spread beyond the borders of China was brought under control in July 2003. According to NHS, there has not been any new case of infection reported worldwide of SARS-COV since 2004.

"During the period of infection, there were 8,098 reported cases of SARS and 774 deaths. This means the virus killed about 1 in 10 people who were infected. People over the age of 65 were particularly at risk, with over a half of those who died from the infection being in this age group," states NHS.

According to WHO, the case fatality rate of SARS varies between 0%-50% depending on the age group affected. The overall estimate case fatality varies from 14%-15%.

There is no cure, specific treatment or vaccine against MERS and SARS.

Hantaviruses are a family of viruses spread mainly by rodents. People get the virus when they inhale air contaminated with the virus. "When fresh rodent urine, droppings, or nesting materials are stirred up, tiny droplets containing the virus get into the air. This process is known as "airborne transmission,"" states CDC.

In rare cases, people can become infected when they're bitten by am infected rodent. Also, a person can get the virus when they touch surfaces contaminated with infected rodent's urine, saliva or droppings.

Hantaviruses are divided into two groups: New World hantaviruses and Old World hantaviruses. New World hantaviruses cause hantavirus pulmonary syndrome (HPS), a severe, sometimes a fatal respiratory disease. Old World hantaviruses cause hemorrhagic fever with renewal syndrome (HFRS).

The occurrence of these diseases is rare.

The mortality rate of HPS is 35-36% while that of HFRS is 1%-15%.

There is no cure, vaccine or special treatment for hantaviruses.