Which is the most dangerous human virus on the planet?

The title of "most dangerous human virus" can depend on several factors, including mortality rate, infectiousness, and the potential for widespread outbreaks. Here are a few of the contenders based on these criteria:

### 1. **Rabies**

- **Mortality Rate:** Nearly 100% once symptoms appear.

- **Transmission:** Typically through the bite of an infected animal.

- **Details:** Rabies is a viral disease that causes acute inflammation of the brain in humans and other mammals. Once clinical symptoms appear, rabies is almost always fatal. Vaccination is effective if given soon after exposure.

### 2. **Ebola Virus**

- **Mortality Rate:** Varies between 25% to 90%, depending on the outbreak and medical care available.

- **Transmission:** Through direct contact with the blood, secretions, organs, or other bodily fluids of infected people, and with surfaces and materials (e.g., bedding, clothing) contaminated with these fluids.

- **Details:** Ebola causes severe hemorrhagic fever, which can lead to death. There have been several outbreaks, primarily in Africa, with high fatality rates.

### 3. **Marburg Virus**

- **Mortality Rate:** Up to 88%.

- **Transmission:** Similar to Ebola, through direct contact with infected bodily fluids.

- **Details:** Marburg virus disease is another type of hemorrhagic fever similar to Ebola and is highly virulent.

### 4. **Hantavirus**

- **Mortality Rate:** 36% for Hantavirus Pulmonary Syndrome (HPS).

- **Transmission:** Primarily through contact with rodent urine, droppings, or saliva.

- **Details:** Hantaviruses can cause severe respiratory disease and hemorrhagic fever with renal syndrome.

### 5. **Smallpox (Variola virus)**

- **Mortality Rate:** Historically, about 30%.

- **Transmission:** Through respiratory droplets and contact with infected individuals or contaminated objects.

- **Details:** Smallpox has been eradicated since 1980 due to an effective global vaccination campaign, but it was once one of the most feared diseases due to its high fatality rate and disfiguring nature.

### 6. **HIV (Human Immunodeficiency Virus)**

- **Mortality Rate:** While antiretroviral therapy has made HIV a manageable condition, untreated, it has a high mortality rate.

- **Transmission:** Through blood, sexual contact, and from mother to child during birth or breastfeeding.

- **Details:** HIV leads to AIDS, which compromises the immune system, making the body vulnerable to a variety of infections and diseases.

### 7. **SARS-CoV-2 (Coronavirus)**

- **Mortality Rate:** Varies widely; overall case fatality rate is estimated to be around 1-2%, but this varies by region, age, and other factors.

- **Transmission:** Through respiratory droplets, airborne transmission, and contact with contaminated surfaces.

- **Details:** The virus responsible for COVID-19 has caused a global pandemic with significant mortality and morbidity, though it generally has a lower fatality rate compared to some of the other viruses listed.

Each of these viruses poses significant risks, but the level of danger can depend on the context, such as availability of medical care, public health measures, and individual immunity.