Bayannur, a city in northern China, was on high alert after a suspected case of Bubonic plague was reported .

The plague is caused by a bacteria called Yersinia pestis, which cause two other diseases — Septicaemic plague and Pneumonic plague. If not treated in time, the bacteria can kill an adult in less than 24 hours, which is transmitted by fleas and rodents. Infected fleas spread the infection to animals, commonly mice, squirrels, prairie dogs and even cats and dogs. Humans get the plague, a zoonotic disease, through direct contact with infected animals or fleas.

Some of the symptoms of the disease include swollen lymph nodes which can be as large as chicken eggs, fever, chills, coughs, fatigue, muscle ache, etc. The swollen lymph nodes are called buboes, which is where the name ‘Bubonic’ comes from. The symptoms for this disease start occurring after an incubation period of 1-7 days.

The plague can cause three different types of infections.

The most common type is the bubonic plague, which represents 80 to 95 percent of cases. The symptoms include fever, chills, weakness, and headache, followed by very painful and swollen lymph nodes, referred to as “buboes.” They usually start two to six days after exposure.

When the plague gets into the blood, it can cause the septicemic plague, which represents 10 to 20 percent of cases, and triggers the entire immune system to fall into a dangerous condition called “sepsis.“

Much less common is the pneumonic plague, which can occur when a bubonic or septicemic plague is not treated and a person’s lungs become infected. It can also be spread through the air from infected humans or animals and can be fatal.

There are over 200 ‘zoonotic’ diseases — infections caused by viruses, bacteria, parasites, fungi or prions that are transferred directly or indirectly to humans from animals.

These include diseases such as animal influenzas, rabies, haemorrhagic fevers such as Ebola, anthrax, the bubonic plague, and ‘mad cow’ disease.

The most recent disease to jump from animals to humans causing a shiver of concern is MERS, or Middle Eastern Respiratory Syndrome, which causes coughing, fever and often fatal pneumonia.

Vertebrate animals such as birds, bats and rats spread a wide range of diseases

The infections can be transferred directly from the animals to humans via contact such as animal bites and scratches, consuming contaminated animal products, breathing in pathogens, or through skin contact.

Insects such as mosquitoes, ticks and flies also transmit a range of diseases from animals to humans including West Nile virus, Lyme disease, bubonic plague and sleeping sickness.

Anthrax

* Bacteria spread by the handling or consumption of infected animals
* Three types: skin (infected through cuts in skin), gastrointestinal (from eating the animal), respiratory (from inhaling spores). The latter is the rarest form.

* It is non-contagious between humans
* Can be treated with antibiotics, prevented with vaccines.
*Until the introduction of vaccines anthrax was major cause of fatal disease in cattle, sheep, goats, camels, horses, and pigs throughout the world.

Bubonic plague

* One of the oldest identifiable diseases
* Widely distributed in the tropics and subtropics.
* Bacteria spread by infected fleas carried on rodents
* Can be treated with antibiotics. Left untreated can kill within 24 hours from pneumonia

Ebola

* First identified in 1976
* West Africa – Democratic Republic of Congo, Republic of Congo, Gabon. Most recent outbreak in Guinea, Liberia and Sierra Leone has killed 672 people to date.

* Fruit bats are thought to be a reservoir of the disease.
*Initial transmission thought to be through handling or consumption of infected animals. Human-to-human transmission happens through direct contact with bodily fluid.
* Causes nausea, vomiting, diarrhoea, internal and external haemorrhaging

* No vaccine yet for humans, but vaccine available for non-human primates
* Can be contained with strict quarantine and health protocol

Hendra

* First identified in 1994 in Queensland, current case in horse in Queensland
* Reservoir is thought to be fruit bats
* Can kill horses, less often dogs and humans
* Causes respiratory infection, brain swelling
* A vaccine is available to prevent hendra in horses