Infectious diseases are illnesses caused by viruses, bacteria, parasites or fungi. They can be passed on in many ways, including through the air, water, food or the bite of another animal. Examples include tuberculosis, malaria and chickenpox. 


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A thoracic aortic aneurysm is a weakened area of a large blood vessel in your chest. It can be very dangerous if it starts to leak or bursts. Here’s how to tell if you have a thoracic aortic aneurysm.

Thoracic aortic aneurysm and dissection

HIV (human immunodeficiency virus) a virus that attacks the immune system, making it harder for you to fight infections. AIDS (acquired immune deficiency syndrome) is a group of potentially life-threatening infections seen in the later stages of HIV infection.


conditions

Boxing gloves and a red ribbon, symbolizing the fight against aids or hiv

HIV is a virus most commonly caught by having unprotected sex or by sharing infected needles and other injecting equipment to inject drugs.

HIV and AIDS

hiv-aids

Careful hand washing stock photo

infectious-diseases

Blood poisoning is a serious infection that occurs when there is bacteria in the blood. It's also known as sepsis and septicaemia. Blood poisoning can be fatal if not treated quickly. 

blood-poisoning

Bacteria are single-celled organisms that can cause an infection if they enter the body. Bacterial infections can affect all parts of the body, including the heart, brain, skin and teeth. They're usually treated with antibiotics.


bacterial-infections

Bacteria are single-celled organisms that can cause an infection if they enter the body. Bacterial infections can affect all parts of the body, including the heart, brain, skin and teeth. They're usually treated with antibiotics.

Sexual health involves being aware of the risks involved in sexual activity and doing what you can to reduce those risks, such as using condoms to help prevent sexually transmitted infections (STIs) and contraceptives to prevent unplanned pregnancies. 

Two condoms on a blue-yellow background- Photo by Reproductive Health Supplies Coalition on Unsplash

reproductive-health-supplies-coalition-udC7xRAWvb4-unsplash

sexual-health

Close- up of open wound with blood on skin of hand stock photo

Sepsis (often referred to as either blood poisoning or septicaemia) is a life-threatening illness caused by the body overreacting to an infection.

Blood poisoning

People Holding Clear Glass Bottle

Antifungal medicines are used to treat fungal infections that often affect the skin and nails. These infections can cause a rash or nail changes, but most can be treated with tablets, creams, gels or sprays.

Cream tube stock photo

Antifungal medicines are used to treat fungal infections.

Woman rinsing and gargling while using mouthwash from a glass

Antifungal medicines

antifungal-medication

A bone infection (osteomyelitis) can occur when an infection in the blood or tissue reaches the bone. A bone infection can also occur if the bone is exposed to germs, such as through injury. Bone infections can be treated using antibiotics or, in some cases, surgery.


Doctor with X-ray

Osteomyelitis is the medical term for a bone infection that is usually caused by bacteria.

Osteomyelitis (bone infection)

bone-infection

Plague is an infectious disease caused by the bacteria Yersinia pestis. This bacteria is carried by animals like rats and fleas. Bubonic plague is a type of plague. Symptoms include a fever, headache and swollen glands.

Photomicrograph of a tissue smear specimen showing the presence of Yersinia pestis bacteria, the pathogen responsible for causing plague. Photo credit: CDC

A recent case of bubonic plague in Inner Mongolia has put what many people think of as a disease of the past back in the spotlight. 

But the reality is that bubonic plague never went away -- cases occur regularly in Mongolia and many other parts of the world. 

Chinese authorities are on alert for more cases, but health experts say the infection does not pose the same global threat it did in the 14th century when it claimed the lives of more than 50 million people during the Black Death.

Here’s what you need to know about the disease.

## What is bubonic plague?

Plague is an infectious disease caused by the bacteria Yersinia pestis, which is carried by small animals, such as rats and squirrels, and the fleas that live on them.

The most common form of the disease is bubonic plague.

## What are the symptoms of bubonic plague?

People with bubonic plague usually develop flu-like symptoms, such as fever, chills, vomiting, nausea and aches, 3 to 7 days after being infected. 

Once a person is infected, the bacteria travel to glands in the body called lymph nodes, where they grow, and cause pain and inflammation. This swollen node is called a ‘bubo’, which is where the name of the disease comes from. 

In some cases, the nodes may develop into open sores. 

If the infection gets worse and spreads to the lungs, it can develop into a condition known as pneumonic plague. People with pneumonic plague may have shortness of breath, coughing and be coughing up blood.

Bubonic plague can also lead to blood poisoning ([septicaemia](/blood-poisoning)) if the bacteria enter the bloodstream.

![Close up image of a rat munching](//images.ctfassets.net/iqo3fk8od6t9/33eVywhDP5JJBMMQN7cb4r/e7f30855cc6a4c9b14028d6ed6bc3616/Close_up_image_of_a_rat_munching.jpg)

## How can you get bubonic plague?

Your chances of catching plague are extremely small, but it’s possible if you’re bitten by an infected flea. This is the most common way people become infected.

People can also be infected if they come into contact with the blood of a dead animal. This can happen, for example, while skinning rabbits or squirrels.

Because bubonic plague is spread through flea bites or direct contact with animal blood, it’s rarely passed from person to person. But if it’s left untreated, spreads to the lungs and develops into pneumonic plague, the infection can be passed between people through droplets in the air.

## How common is bubonic plague?

There have been global outbreaks of plague in the past -- the most famous of which was the historic Black Death, which killed more than 50 million people during the 14th century. 

It’s much less common today, but still occurs worldwide. 

According to the World Health Organization (WHO), most cases today are reported in 3 countries: Madagascar, Democratic Republic of Congo and Peru. Madagascar reports cases of plague almost every year and a large outbreak in 2017 led to more than 2,400 cases. 

Many other countries, including Mongolia and the USA, have cases of plague.

Records of the number of people infected are limited, but 3,248 cases were reported to the WHO between 2010 and 2015. This included 584 deaths.

![Anteroposterior chest x-ray, revealed what appeared to be normal bilateral lung fields. Caused by a case of pneumonic plague, due to a Yersinia pestis bacterial infection. Image Credit: CDC](//images.ctfassets.net/iqo3fk8od6t9/1cM0S7q7c0p6e4zsAUauWy/3ff7f24dc9bfdd753e0c510ab7c9685a/Anteroposterior__AP__chest_x-ray__revealed_what_appeared_to_be_normal_bilateral_lung_fields.jpg)

## Can bubonic plague be treated?

Bubonic plague can be treated with antibiotics if it’s caught early enough. This is 1 of the reasons why an outbreak of plague today is unlikely to lead to the type of epidemic seen during the Black Death, as antibiotics didn’t exist in the 14th century. 

People are less likely to reach the stage where the infection gets to the lungs and can spread to other people. 

There’s also a vaccine for plague, but it’s only given to people at high risk of getting the infection as part of their job, such as healthcare workers and lab staff.

## Is plague fatal?

Plague is a serious infection that can kill 30% to 60% of people who catch it and don’t get treatment. The pneumonic form of the disease is always fatal without treatment.

## Will there be a global outbreak of plague?

Outbreaks of plague still occur in some parts of the world, but experts say it’s unlikely that any outbreak will become a global threat.

“While plague causes severe illness, if it is recognised promptly then it can be easily treated with antibiotics, and patients will make a full recovery,” said Jimmy Whitworth, Professor of International Public Health, London School of Hygiene & Tropical Medicine (LSHTM). 

“Two cases of plague were identified in Beijing last year in travellers from Mongolia and were quickly treated, with no further spread of infection.”

A recent outbreak of the bubonic plague in Inner Mongolia has put the disease back in the spotlight, but experts caution that it’s unlikely to become a global threat. Here’s what you need to know.



Bubonic plague: What you need to know

bubonic-plague

Chickenpox and shingles are infections caused by the varicella zoster virus. Chickenpox usually affects children aged 10 or younger. Shingles is caused by reactivation of the virus many years after having chickenpox. Both conditions can cause an itchy rash and blisters. 


Mother taking care of little girl with chicken pox

Chickenpox is a mild and common childhood illness that most children catch at some point.

Chickenpox

chickenpox-shingles

A fever is when your body temperature rises to 38C or higher. This is also known as having a high temperature and it can be caused by many things, including an infection. If you have a fever you should rest and stay hydrated.

Young woman feeling symptoms of an illness

fever

The herpes simplex virus, also known as HSV, is the virus that causes herpes. Two types exist: herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). 

Female face with herpes on the lips

Genital herpes is a sexually transmitted infection thats causes blisters on the genitals and can be controlled by medication.

Genital herpes

herpes

Lyme disease is a bacterial infection caused by being bitten by an infected tick. If you have Lyme disease, you may develop a red circle-shaped rash around the site of the tick bite up to a few weeks after being bitten. Lyme disease can cause a wide variety of symptoms, which can change depending on the stage of the infection.


Castor bean tick 

Lyme disease is a bacterial infection that is spread to humans by infected ticks. Ticks are small arachnids that feed on the blood of mammals, including humans.

Lyme disease

lyme-disease

Malaria is an infectious disease that's passed to humans by infected mosquito. Symptoms, such as muscle aches and being sick, tend to develop days or weeks after you've been bitten by a mosquito. Malaria is a serious infection that needs urgent treatment.  


Mosquito sitting on human skin

Malaria is a tropical disease spread by female Anopheles mosquitoes that are infected by Plasmodium parasites. If not diagnosed and treated promptly, it can be fatal.

Parasites are organisms that survive by living off another organism, known as a 'host'. Parasite infections are more common in tropical parts of the world, and include malaria and gut infections, like giardiasis.


parasite-infection

Malaria

malaria

Parasitic hookworm Ancylosoma (credit - Dr_Microbe)

Severe acute respiratory syndrome (SARS) is an infection of the airways that was first seen in humans in 2003. It’s caused by the SARS coronavirus (SARS CoV). Middle East respiratory syndrome coronavirus (MERS) is a respiratory illness that was first reported in 2012. 

Viruses in human lungs, 3D illustration, conceptual image for flu, MERS-CoV and SARS

Viruses in human lungs, 3D illustration, conceptual image for flu, MERS-CoV and SARS (credit - Dr_Microbe)

sars-mers

Tuberculosis is an infectious disease caused by a bacterium called Mycobacterium tuberculosis. Tuberculosis mainly affects the lungs, but it can also affect your brain, bones and nervous system. 


Young Female Doctor listening with stethoscope on patient's back 

Tuberculosis (TB) is a curable bacterial infection spread by inhaling tiny droplets from the coughs or sneezes of an infected person.

Tuberculosis (TB) 

tuberculosis

Viral infections are caused by germs called viruses. These tiny organisms invade and damage the cells of the body. The symptoms you may notice when you have a viral infection are caused by this damage and your body fighting the virus. Common examples of viral infections include chickenpox and the common cold. 


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