Which viruses are incurable

Humans have been battling viruses since before our species had even evolved into its modern form. For some viral diseases, vaccines and antiviral drugs have allowed us to keep infections from spreading widely, and have helped sick people recover. For one disease — smallpox — we've been able to eradicate it, ridding the world of new cases. But we're a long way from winning the fight against viruses. In recent decades, several viruses have jumped from animals to humans and triggered sizable outbreaks, claiming thousands of lives.

Related: 20 of the worst epidemics and pandemics in history. But there are other viruses out there that are equally deadly, and some that are even deadlier. Some viruses, including the novel coronavirus currently driving outbreaks around the globe, have lower fatality rates, but still pose a serious threat to public health as we don't yet have the means to combat them. Here are the 12 worst killers, based on the likelihood that a person will die if they are infected with one of them, the sheer numbers of people they have killed, and whether they represent a growing threat.

Scientists first identified the Marburg virus in , when small outbreaks occurred among lab workers in Germany who were exposed to infected monkeys imported from Uganda, according to the World Health Organization WHO. Marburg virus symptoms are similar to Ebola in that both viruses can cause hemorrhagic fever, meaning that infected people develop high fevers, and bleeding throughout the body that can lead to shock, organ failure and death, according to Mayo Clinic.

The first known Marburg virus outbreak in West Africa was confirmed in August The case was a male from south-western Guinea, who developed a fever, headache, fatigue, abdominal pain and gingival hemorrhage.

This outbreak lasted for six weeks and, while there were high-risk contacts, only one case was confirmed, according to Reuters. The first known Ebola outbreaks in humans struck simultaneously in the Republic of the Sudan and the Democratic Republic of Congo in Ebola is spread through contact with blood or other body fluids, or tissue from infected people or animals.

The known strains vary dramatically in their deadliness, Elke Muhlberger, an Ebola virus expert and associate professor of microbiology at Boston University, told Live Science. The outbreak underway in West Africa began in early , and is the largest and most complex outbreak of the disease to date, according to WHO. In December , the Ervebo vaccine was approved by the U. Food and Drug administration. This vaccine helps to defend against the Zaire ebola virus and a global stockpile became available from January Although rabies vaccines for pets — introduced in the s — have helped make the disease exceedingly rare in the developed world, this condition remains a serious problem in India and parts of Africa.

Infection from this virus develops after a bite or scratch from an infected animal. This can result in damage to the brain and nerves. In the modern world, the deadliest virus of all may be HIV. Amesh Adalja, an infectious disease physician and spokesman for the Infectious Disease Society of America.

An estimated 32 million people have died from HIV since the disease was first recognized in the early s. Powerful antiviral drugs have made it possible for people to live for years with HIV.

In , there were , HIV-related deaths worldwide. In , the World Health Assembly declared the world free of smallpox. When it reproduces, particles spread to new cells and new hosts. The features of a virus affect its ability to spread. Some viruses can remain active on an object for some time. If a person with the virus on their hands touches an item, the next person can pick up that virus by touching the same object. The object is known as a fomite. Viruses often change over time.

Some of these changes are very small and do not cause concern, but others can be more significant. Significant changes could make a virus more transmissible, as has been the case with the B. They may also help the virus evade the immune system or existing treatments.

For example, doctors use several drugs in combination to treat HIV so that it is harder for the virus to develop resistance to treatment. Influenza viruses can also do so-called antigenic shift. This can happen if a host cell has become infected with two different types of influenza virus.

For instance, pigs can often serve as a mixing vessel for avian and human influenza viruses. Some viruses, such as HPV, can lead to cancer. The full impact of a virus can take time to appear, and sometimes there may be a secondary effect.

For example, the herpes zoster virus can cause chickenpox. The person recovers, but the virus may stay in the body. Years later, it may cause shingles in the same individual. Coronaviruses are a large family of viruses and include viruses that cause the common cold.

However, it has changed many times since scientists first identified it in China. By September , scientists had logged over 12, mutations, and the development continues. Some variants are more transmissible and more likely to cause severe illness than others. The main concern with new variants is the unpredictability of their impact.

The main symptoms of COVID are dry cough , fatigue , and fever, but there are many possible symptoms. Anyone who has symptoms should seek a test. It is also important to self-isolate until 10 days after symptoms appear and when no fever has been present for 24 hours. If a person has difficulty breathing , they should seek emergency medical attention. However, special T cells, known as cytotoxic T cells, can recognize cells that contain viruses, and release substances that kill those cells.

Some viruses can escape detection by cytotoxic T cells, but other immune cells — natural killer cells — can cause the cell containing the virus to die. In addition, body cells that contain a virus emit proteins called interferons, which warn other cells that a virus is present.

This gives healthy cells a chance to defend themselves by changing the molecular makeup of their surface. Antibodies can also help fight a virus before it enters a cell. They do this by neutralizing or damaging the virus or by changing its features so that it can no longer enter healthy cells. Antibiotics treat bacterial infections , but they cannot treat a viral infection.

People will need either a vaccination to prevent infection, or antiviral drugs to treat any symptoms. Sometimes, the only option is symptom relief. In recent decades, scientists have developed antiviral drugs, largely in response to the AIDS pandemic.

These drugs do not destroy the virus, but they slow or prevent its development. With antiviral treatment for HIV, for example, the level of virus in the body can become so low that tests cannot detect it. July Retrieved 23 April Newnham, Evan D Journal of Gastroenterology and Hepatology. Presentation of CD with malabsorptive symptoms or malnutrition is now the exception rather than the rule. United European Gastroenterology Journal Review.

Fasano A, Catassi C December Celiac disease". The New England Journal of Medicine. Bold J, Rostami K Gastroenterol Hepatol Bed Bench. Clinical Gastroenterology Review. Medicine Baltimore Meta-Analysis. BMJ Review. It can cause a wide variety of symptoms, both intestinal and extra-intestinal because it is a systemic autoimmune disease that is triggered by dietary gluten.

Nature Reviews. Current Opinion in Oncology. March Archived from the original on 26 August Archived from the original PDF on Robson, David 19 January BBC Future. Schenkein J, Montagna P Part 1: what is FFI? ISSN Lessons of formation, repair, and bone bioengineering". Organogenesis Review. World Journal of Gastroenterology. Ohgaki H, Kleihues P May The American Journal of Pathology. Annals of Neurology. Retrieved Beauman, J. American Family Physician.