Marburg virus Marburg virus disease is a highly virulent disease that causes haemorrhagic fever, with a fatality ratio of up to 88%. It ...
Marburg virus disease is a highly virulent disease that causes haemorrhagic fever, with a fatality ratio of up to 88%. It is in the same family as the virus that causes Ebola virus disease.
Two large outbreaks that occurred simultaneously in Marburg and Frankfurt in Germany, and in Belgrade, Serbia, in 1967, led to the initial recognition of the disease. The outbreak was associated with laboratory work using African green monkeys (Cercopithecus aethiops) imported from Uganda. Subsequently, outbreaks and sporadic cases have been reported in Angola, Democratic Republic of the Congo, Kenya, South Africa (in a person with recent travel history to Zimbabwe) and Uganda. In 2008, two independent cases were reported in travelers who visited a cave inhabited by Rousettus bat colonies in Uganda.
Marburg viru |
Human infection with Marburg virus disease initially results
from prolonged exposure to mines or caves inhabited by Rousettus bat colonies.
Once an individual is infected with the virus, Marburg can spread through
human-to-human transmission via direct contact (through broken skin or mucous
membranes) 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.
incubation period: The incubation period for Marburg virus disease varies from 2 to 21 days
Illness caused by Marburg virus begins abruptly, with high fever, severe headache and severe malaise. Muscle aches and pains are a common feature. Severe watery diarrhoea, abdominal pain and cramping, nausea and vomiting can begin on the third day. Diarrhoea can persist for a week. The appearance of patients at this phase has been described as showing “ghost-like” drawn features, deep-set eyes, expressionless faces and extreme lethargy. A non-itchy rash has been noted between 2 and 7 days after the onset of symptoms.
Many patients develop severe haemorrhagic manifestations within 7 days, and fatal cases usually have bleeding, often from multiple areas. Fresh blood in vomitus and faeces is often accompanied by bleeding from the nose, gums and vagina. Spontaneous bleeding at venepuncture sites (where intravenous access is obtained to give fluids or obtain blood samples) can be particularly troublesome. During the severe phase of illness, patients have sustained high fevers. Involvement of the central nervous system can result in confusion, irritability and aggression. Orchitis (inflammation of the testicles) has been reported occasionally in the late phase (15 days).
In fatal cases, death usually occurs between 8 and 9 days after onset, usually preceded by severe blood loss and shock.
There is as yet no proven treatment available for Marburg virus disease. However, a range of potential treatments including blood products, immune therapies and drug therapies are currently being evaluated. Supportive care – rehydration with oral or intravenous fluids – and treatment of specific symptoms improves survival.
It can be difficult to clinically distinguish Marburg virus disease (MVD) from other infectious diseases such as malaria, typhoid fever, shigellosis, meningitis and other viral haemorrhagic fevers. Confirmation that symptoms are caused by Marburg virus infection are made using the following diagnostic methods:
antibody enzyme-linked immunosorbent assay (ELISA);
antigen detection tests;
serum neutralization tests;
reverse-transcriptase polymerase chain reaction (RT-PCR) assay; and
virus isolation by cell culture.
Samples collected from patients are an extreme biohazard risk and laboratory testing on non-inactivated samples need to be conducted under maximum biological containment conditions. All biological specimens must be packaged using the triple packaging system when transported nationally and internationally.
Ebola virus disease (EVD), formerly known as Ebola haemorrhagic fever, is a severe, often fatal illness affecting humans and other primates.
The virus is transmitted to people from wild animals (such as fruit bats, porcupines and non-human primates) and then spreads in the human population 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.
Ebola virus |
The average EVD case fatality rate is around 50%. Case fatality rates have varied from 25% to 90% in past outbreaks.
The first EVD outbreaks occurred in remote villages in Central Africa, near tropical rainforests. The 2014–2016 outbreak in West Africa was the largest and most complex Ebola outbreak since the virus was first discovered in 1976. There were more cases and deaths in this outbreak than all others combined. It also spread between countries, starting in Guinea then moving across land borders to Sierra Leone and Liberia.
It is thought that fruit bats of the Pteropodidae family are natural Ebola virus hosts.
The incubation period, that is, the time interval from infection with the virus to onset of symptoms, is from 2 to 21 days. A person infected with Ebola cannot spread the disease until they develop symptoms.
Symptoms of EVD can be sudden and include: fever, fatigue, muscle, pain, headache, and sore throat. This is followed by vomiting, diarrhea, rash, symptoms of impaired kidney and liver function, and in some cases internal and external bleeding (e.g. oozing from the gums, blood in the stools). Laboratory findings include low white blood cell and platelet counts and elevated liver enzymes.
It can be difficult to clinically distinguish EVD from other infectious diseases such as malaria, typhoid fever and meningitis. A range of diagnostic tests have been developed to confirm the presence of the virus.
Treatment and Prevention
There is no proven treatment for Ebola but simple interventions early on can significantly improve chances of survival. This includes rehydration with fluids and body salts (given orally or intravenously), and treatment of specific symptoms such as low blood pressure, vomiting, diarrhea and infections.A range of potential treatments including blood products, immune therapies and drug therapies are currently being evaluated.
Hand hygiene is the most effective way to prevent the spread of the Ebola virus.
An experimental Ebola vaccine known as rVSV-ZEBOV proved highly protective against the deadly virus in a major trial in Guinea in 2015. It is being used in response to the current outbreak in the Democratic Republic of the Congo using a ring vaccination protocol.
During an outbreak, health partners apply a package of interventions including case management, surveillance, contact tracing, laboratory testing, safe burials and community engagement.
Working with communities to reduce risk factors for Ebola transmission is critical to controlling outbreaks.
Rabies is a viral zoonotic disease that causes progressive and fatal inflammation of the brain and spinal cord. Clinically, it has two forms:
Furious rabies – characterized by hyperactivity and hallucinations.
Paralytic rabies – characterized by paralysis and coma.
Although fatal once clinical signs appear, rabies is entirely avoidable; vaccines, medicines and technologies have long been available to prevent death from rabies. Nevertheless, rabies still kills tens of thousands of people each year. Of these cases, approximately 99% are acquired from the bite of an infected dog.
Dog-mediated human rabies can be eliminated by tackling the disease at its source: infected dogs. Making people aware of how to avoid the bites of rabid dogs, to seek treatment when bitten and to vaccinate animals can successfully disrupt the rabies transmission cycle.
Rabies is estimated to cause 59 000 human deaths annually in over 150 countries, with 95% of cases occurring in Africa and Asia. Due to underreporting and uncertain estimates, this number is likely a gross underestimate. The burden of disease is disproportionally borne by rural poor populations, with approximately half of cases attributable to children under 15 years of age.
Early symptoms of a rabies infection can include a fever with pain and unusual or unexplained tingling, pricking or burning sensation (paraesthesia) at the wound site. In later states, the virus spreads to the central nervous system, causing fatal inflammation of the brain and spinal cord. The incubation period of the disease can vary from 1 week to 1 year, though it is typically 2–3 months.
The two types of rabies show different symptoms. Furious rabies causes signs of hyperactivity, excitable behaviour, hydrophobia (fear of water) and sometimes aerophobia (fear of drafts or of fresh air). Death occurs after a few days due to cardio-respiratory arrest.
Paralytic rabies, which accounts for about 20% of the total number of human cases, runs a less dramatic and usually longer course than the furious form. Muscles gradually become paralyzed, starting at the site of the bite or scratch. A coma slowly develops and eventually death occurs. The paralytic form of rabies is often misdiagnosed, contributing to the under-reporting of the disease.
Vaccinating dogs is the most cost-effective strategy for preventing rabies in people, and human rabies vaccines exist for pre-exposure immunization.
If you are bitten or scratched by an animal, particularly a dog:
Wash the wound immediately with soap or detergent.
Flush the wound thoroughly for about 15 minutes with copious amounts of water.
Apply an iodine-containing or anti-viral medication to the wound 15 minutes after it has been washed and flushed.
Avoid applying irritants to the wounds such as chili powder, plant juices, acids and alkalis.
Avoid covering the wound with dressings or bandages.
Seek transportation to a health care facility for further assessment and treatment by a healthcare professional.
If possible, safely confine the biting animal and collect information on it and the bite circumstance to provide to the health care professional and public health officer. Keep the biting animal confined and under observation for 10 days.
WHO continues to promote human rabies prevention through the elimination of rabies in dogs, dog bite prevention strategies, and more widespread use of the intradermal route for post-exposure prophylaxis, which reduces volume and therefore the cost of cell-cultured vaccine by 60% to 80%.
Human immunodeficiency virus (HIV) is an infection that attacks the body’s immune system, specifically the white blood cells called CD4 cells. HIV destroys these CD4 cells, weakening a person’s immunity against infections such as tuberculosis and some cancers.WHO recommends that every person who may be at risk of HIV should access testing. People diagnosed with HIV should be offered and linked to antiretroviral treatment as soon as possible following diagnosis. If taken consistently, this treatment also prevents HIV transmission to others.
If the person’s CD4 cell count falls below 200, their immunity is severely compromised, leaving them more susceptible to infections. Someone with a CD4 count below 200 is described as having AIDS (acquired immunodeficiency syndrome).
HIV is fully preventable. Effective antiretroviral treatment prevents HIV transmission from mother to child during pregnancy, delivery and breastfeeding. Someone who is on antiretroviral therapy (ART) and virally suppressed will not pass HIV to their sexual partners.
There are many ways to prevent HIV. Condoms prevent HIV, other sexually transmitted infections and unplanned pregnancies. Pre- and post-exposure prophylaxis use antiretroviral medicines to prevent HIV. Male circumcision is recommended for men and adolescent boys in high-burden countries in eastern and southern Africa. Harm reduction (needle syringe programmes and opioid substitution therapy) prevents HIV and other blood-borne infections for people who inject drugs. WHO recommends packages of services tailored to various populations, including for the 5 key populations (men who have sex with men, people who inject drugs, people in prisons, sex workers and transgender populations), who are particularly vulnerable to HIV.
HIV can be diagnosed using simple and affordable rapid diagnostic tests, as well as self-tests. It is important that HIV testing services follow the 5Cs: consent, confidentiality, counselling, correct results and connection with treatment and other services.
Treatment and Care
HIV is treated with antiretroviral therapy (ART) consisting of one or more medicines. ART does not cure HIV, but reduces replication of the virus in the blood, thereby reducing the viral load to an undetectable level.
ART enables people living with HIV to lead healthy, productive lives. It also works as an effective prevention, reducing the risk of onward transmission by 96%.
ART should be taken every day throughout the person’s life. People can continue with safe and effective ART if they adhere to their treatment. In cases when ART becomes ineffective due to reasons such as lost contact with health care providers and drug stockouts, people will need to switch to other medicines to protect their health.
Smallpox is an ancient disease caused by the variola virus. Early symptoms include high fever and fatigue. The virus then produces a characteristic rash, particularly on the face, arms and legs. The resulting spots become filled with clear fluid and later, pus, and then form a crust, which eventually dries up and falls off. Smallpox was fatal in up to 30% of cases.
Smallpox has existed for at least 3000 years and was one of the world’s most feared diseases until it was eradicated by a collaborative global vaccination programme led by the World Health Organization. The last known natural case was in Somalia in 1977. Since then, the only known cases were caused by a laboratory accident in 1978 in Birmingham, England, which killed one person and caused a limited outbreak. Smallpox was officially declared eradicated in 1979.
Smallpox no longer occurs naturally since it was totally eradicated by a lengthy and painstaking process, which identified all cases and their contacts and ensured that they were all vaccinated. Until then, smallpox killed many millions of people.
The virus which causes smallpox is contagious and spreads through person-to- person contact and saliva droplets in an infected person’s breath. It has an incubation period of between 7 and 17 days after exposure and only becomes infectious once the fever develops. A distinctive rash appears two to three days later. The most infectious period is during the first week of illness, although a person with smallpox is still infectious until the last scabs fall off.
The speed of smallpox transmission is generally slower than for such diseases as measles or chickenpox. Patients spread smallpox primarily to household members and friends because by the time patients are contagious, they are usually sick and stay in bed; large outbreaks in schools were uncommon.
There is no cure for smallpox, but vaccination can be used very effectively to prevent infection from developing if given during a period of up to four days after a person has been exposed to the virus. This is the strategy that was used to eradicate the disease during the 20th century. New antiviral drugs, that have been developed for other diseases since smallpox was eradicated, may have a role. No studies of their usefulness, or safety, have been conducted on humans exposed to smallpox.
This image shows the hantavirus known as the Sin Nombre virus (SNV), under a transmission electron microscope. This virus caused an outbreak in November 1993, in the Four Corners region of the U.S.(Image credit: Cynthia Goldsmith. Provided by CDC/ Brian W.J. Mahy, PhD; Luanne H. Elliott, M.S.)
Hantavirus pulmonary syndrome (HPS) first gained wide attention in the U.S. in 1993, when a healthy, young Navajo man and his fiancée living in the Four Corners area of the United States died within days of developing shortness of breath. A few months later, health authorities isolated hantavirus from a deer mouse living in the home of one of the infected people. More than 600 people in the U.S. have now contracted HPS, and 36% have died from the disease, according to the Centers for Disease Control and Prevention.
The virus is not transmitted from one person to another, rather, people contract the disease from exposure to the droppings of infected mice.
Previously, a different hantavirus caused an outbreak in the early 1950s, during the Korean War, according to a 2010 paper in the journal Clinical Microbiology Reviews. More than 3,000 troops became infected, and about 12% of them died.
While the virus was new to Western medicine when it was discovered in the U.S., researchers realized later that Navajo medical traditions describe a similar illness, and linked the disease to mice.
This digitally-colorized image shows the H1N1 influenza virus under a transmission electron microscope. In 2009, this virus (then called the swine flu) caused a pandemic, and is thought to have killed 200,00 people worldwide.(Image credit: National Institute of Allergies and Infectious Diseases (NIAID))
During a typical flu season, up to 500,000 people worldwide will die from the illness, according to WHO. But occasionally, when a new flu strain emerges, a pandemic results with a faster spread of disease and, often, higher mortality rates.
The most deadly flu pandemic, sometimes called the Spanish flu, began in 1918 and sickened up to 40% of the world's population, killing an estimated 50 million people.
"I think that it is possible that something like the 1918 flu outbreak could occur again," Muhlberger said. "If a new influenza strain found its way in the human population, and could be transmitted easily between humans, and caused severe illness, we would have a big problem."
Dengue virus first appeared in the 1950s in the Philippines and Thailand, and has since spread throughout the tropical and subtropical regions of the globe. Up to 40% of the world's population now lives in areas where dengue is endemic, and the disease — with the mosquitoes that carry it — is likely to spread farther as the world warms.
Dengue sickens 50 to 100 million people a year, according to WHO. Although the mortality rate for dengue fever is lower than some other viruses, at 2.5%, the virus can cause an Ebola-like disease called dengue hemorrhagic fever, and that condition has a mortality rate of 20% if left untreated. "We really need to think more about dengue virus because it is a real threat to us," Muhlberger said.
A vaccine for Dengue was approved in 2019 by the U.S. Food and Drug Administration for use in children 9-16 years old living in an areas where dengue is common and with a confirmed history of virus infection, according to the CDC. In some countries, an approved vaccine is available for those 9-45 years old, but again, recipients must have contracted a confirmed case of dengue in the past. Those who have not caught the virus before could be put at risk of developing severe dengue if given the vaccine.
Two vaccines are now available to protect children from rotavirus, the leading cause of severe diarrheal illness among babies and young children. The virus can spread rapidly, through what researchers call the fecal-oral route (meaning that small particles of feces end up being consumed).
Although children in the developed world rarely die from rotavirus infection, the disease is a killer in the developing world, where rehydration treatments are not widely available.
The WHO estimates that worldwide, 453,000 children younger than age 5 died from rotavirus infection in 2008. But countries that have introduced the vaccine have reported sharp declines in rotavirus hospitalizations and deaths.
The virus that causes severe acute respiratory syndrome, or SARS, first appeared in 2002 in the Guangdong province of southern China, according to the WHO. The virus likely emerged in bats, initially, then hopped into nocturnal mammals called civets before finally infecting humans. After triggering an outbreak in China, SARS spread to 26 countries around the world, infecting more than 8000 people and killing more than 770 over the course of two years.
The disease causes fever, chills and body aches, and often progresses to pneumonia, a severe condition in which the lungs become inflamed and fill with pus. SARS has an estimated mortality rate of 9.6%, and as of yet, has no approved treatment or vaccine. However, no new cases of SARS have been reported since the early 2000s, according to the CDC.
Middle East respiratory syndrome (MERS) is a viral respiratory illness caused by a coronavirus (Middle East respiratory syndrome coronavirus, or MERS‐CoV) that was first identified in Saudi Arabia in 2012.
Coronaviruses are a large family of viruses that can cause diseases in humans, ranging from the common cold to Severe Acute Respiratory Syndrome (SARS).
A typical case of MERS includes fever, cough, and/or shortness of breath. Pneumonia is common, however some people infected with the MERS virus have been reported to be asymptomatic. Gastrointestinal symptoms, including diarrhoea, have also been reported.
Severe cases of MERS can include respiratory failure that requires mechanical ventilation and support in an intensive-care unit.
Some patients have had organ failure, especially of the kidneys, or septic shock. The virus appears to cause more severe disease in people with weakened immune systems, older people, and people with chronic diseases as diabetes, cancer, and chronic lung disease.
The mortality rate for people with the MERS virus is approximately 35% – this may be an overestimate however, as mild cases may be missed by existing surveillance systems.
What is a coronavirus?
Coronaviruses are a large family of viruses which may cause illness in animals or humans. In humans, several coronaviruses are known to cause respiratory infections ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS). The most recently discovered coronavirus causes coronavirus disease COVID-19.
What is COVID-19?
COVID-19 is the infectious disease caused by the most recently discovered coronavirus. This new virus and disease were unknown before the outbreak began in Wuhan, China, in December 2019. COVID-19 is now a pandemic affecting many countries globally.
What are the symptoms of COVID-19?
The most common symptoms of COVID-19 are fever, dry cough, and tiredness. Other symptoms that are less common and may affect some patients include aches and pains, nasal congestion, headache, conjunctivitis, sore throat, diarrhea, loss of taste or smell or a rash on skin or discoloration of fingers or toes. These symptoms are usually mild and begin gradually. Some people become infected but only have very mild symptoms.
Most people (about 80%) recover from the disease without needing hospital treatment. Around 1 out of every 5 people who gets COVID-19 becomes seriously ill and develops difficulty breathing. Older people, and those with underlying medical problems like high blood pressure, heart and lung problems, diabetes, or cancer, are at higher risk of developing serious illness. However, anyone can catch COVID-19 and become seriously ill. People of all ages who experience fever and/or cough associated withdifficulty breathing/shortness of breath, chest pain/pressure, or loss of speech or movement should seek medical attention immediately. If possible, it is recommended to call the health care provider or facility first, so the patient can be directed to the right clinic.
What should I do if I have COVID-19 symptoms and when should I seek medical care?
If you have minor symptoms, such as a slight cough or a mild fever, there is generally no need to seek medical care. Stay at home, self-isolate and monitor your symptoms. Follow national guidance on self-isolation.
However, if you live in an area with malaria or dengue fever it is important that you do not ignore symptoms of fever. Seek medical help. When you attend the health facility wear a mask if possible, keep at least 1 metre distance from other people and do not touch surfaces with your hands. If it is a child who is sick help the child stick to this advice.
Seek immediate medical care if you have difficulty breathing or pain/pressure in the chest. If possible, call your health care provider in advance, so he/she can direct you to the right health facility.
How does COVID-19 spread?
People can catch COVID-19 from others who have the virus. The disease spreads primarily from person to person through small droplets from the nose or mouth, which are expelled when a person with COVID-19 coughs, sneezes, or speaks. These droplets are relatively heavy, do not travel far and quickly sink to the ground. People can catch COVID-19 if they breathe in these droplets from a person infected with the virus. This is why it is important to stay at least 1 meter) away from others. These droplets can land on objects and surfaces around the person such as tables, doorknobs and handrails. People can become infected by touching these objects or surfaces, then touching their eyes, nose or mouth. This is why it is important to wash your hands regularly with soap and water or clean with alcohol-based hand rub.
WHO is assessing ongoing research on the ways that COVID-19 is spread and will continue to share updated findings.
Can COVID-19 be caught from a person who has no symptoms?
COVID-19 is mainly spread through respiratory droplets expelled by someone who is coughing or has other symptoms such as fever or tiredness. Many people with COVID-19 experience only mild symptoms. This is particularly true in the early stages of the disease. It is possible to catch COVID-19 from someone who has just a mild cough and does not feel ill.
Some reports have indicated that people with no symptoms can transmit the virus. It is not yet known how often it happens. WHO is assessing ongoing research on the topic and will continue to share updated findings.
How can we protect others and ourselves if we don't know who is infected?
Practicing hand and respiratory hygiene is important at ALL times and is the best way to protect others and yourself.
When possible maintain at least a 1 meter distance between yourself and others. This is especially important if you are standing by someone who is coughing or sneezing. Since some infected persons may not yet be exhibiting symptoms or their symptoms may be mild, maintaining a physical distance with everyone is a good idea if you are in an area where COVID-19 is circulating.
Is there a vaccine, drug or treatment for COVID-19?
While some western, traditional or home remedies may provide comfort and alleviate symptoms of mild COVID-19, there are no medicines that have been shown to prevent or cure the disease. WHO does not recommend self-medication with any medicines, including antibiotics, as a prevention or cure for COVID-19. However, there are several ongoing clinical trials of both western and traditional medicines. WHO is coordinating efforts to develop vaccines and medicines to prevent and treat COVID-19 and will continue to provide updated information as soon research results become available.
The most effective ways to protect yourself and others against COVID-19 are to:
Clean your hands frequently and thoroughly
Avoid touching your eyes, mouth and nose
Cover your cough with the bend of elbow or tissue. If a tissue is used, discard it immediately and wash your hands.
Maintain a distance of at least 1 metre from others.
How long does it take after exposure to COVID-19 to develop symptoms?
The time between exposure to COVID-19 and the moment when symptoms start is commonly around five to six days but can range from 1 – 14 days.
How long does the virus survive on surfaces?
The most important thing to know about coronavirus on surfaces is that they can easily be cleaned with common household disinfectants that will kill the virus. Studies have shown that the COVID-19 virus can survive for up to 72 hours on plastic and stainless steel, less than 4 hours on copper and less than 24 hours on cardboard.
As, always clean your hands with an alcohol-based hand rub or wash them with soap and water. Avoid touching your eyes, mouth, or nose.
Are antibiotics effective in preventing or treating COVID-19?
No. Antibiotics do not work against viruses; they only work on bacterial infections. COVID-19 is caused by a virus, so antibiotics do not work. Antibiotics should not be used as a means of prevention or treatment of COVID-19. In hospitals physicians will sometimes use antibiotics to prevent or treat secondary bacterial infections which can be a complication of COVID-19 in severely ill patients. They should only be used as directed by a physician to treat a bacterial infection.