The most rare disease is smallpox. In May 1978, the World Health Organization registered zero cases in the previous six months worldwide

Most Resurgent Disease

The Soviet Union’s collapse led to crumbling health services, accelerating the spread of diptheria. With 2,000 cases in 1991, the International Red Cross estimates that there were 150,000 to 200,000 cases in the former USSR countries in 1997.

Fastest Growing Disease

The UN AIDS report of December, 1998, states that 5.8 million new cases of HIV infection occurred that year, at the rate of 11 people per minute. Since 1997, the number of people living with the virus had risen by 10%, to 33.4 million worldwide. India holds the record for the country with the largest HIV infected population, with an estimated 4 million HIV positive people. In the worst affected state, Tamil Nadu (population, 25 million), a new survey revealed that half a million are infected with HIV and that the infection rate is three times higher in villages than in cities.

Most Common Noncontagious disease

Periodontal diseases like gingivitis are the world's more prevalent noncontagious disease

Worst Flesh-eating disease

Dubbed the " flesh eating bug" by the media in May 194, the rare and deadly necrotizing fasciitis (NF, has been around since WW I . The cunning streptococcus a bacteria firsts attacks a layer of tissue below the skin, leaving gangrene in its wake, for which there is only one cure- surgical removal of the infected area.

Leprosy is the world's oldest disease, with cases found as far back as 1350 BC. The disease usually starts as a patch of skin that becomes insensitive to pain, touch, and temperature. This is caused by the bacterium Mycobacterium leprae. Leprosy is an infectious disease directly transmitted from man to man.
 

Deadliest Avian Flu Outbreak

Avian flu, a strain of influenza previously only known to affect birds, was found to have infected 16 people in Hong Kong, China, in 1997. Four people died from the virus, which is the first to have been passed directly from birds to humans.

Fewest Physicians Per Population

Malawi is the country with the fewest physicians per capita, with one for every 49,118 people. The country with the smallest number of people per physician is Monaco with 169.
 

Most Beneficial Parasite To Humans

The squirm-worthy leech (Hirudo medicinalis) was favored for its bloodsucking powers back in the 19th century. Due to the healing properties of its saliva the leech has wormed its way back into medicine - and into the record books as the most beneficial parasite for humans! In 1991, a team of Canadian surgeons led by Dr Dean Vistnes, took advantage of the anticoagulants in leeches' saliva to drain away blood and prevent it from clotting during an operation to reattach a patient's scalp. The animals used in this procedure had been specially cultured in sterile conditions.
 

The west African island-republic of Sao Tome and Principe has 241 deaths per 100,000 per annum due to infectious diseases.

Newest Disease

The new variant of Creutzfeldt-Jakob disease (CJD) first reared its ugly head in the UK in the 1990s, together with its partner-in-crime BSE (Mad Cow Disease). CJD, which leads to dementia and a physical breakdown in humans, is the result of eating infected cow's meat. It's enough to put you off your burger and it did - all cattle exports were banned from the UK in 1996. Five million cows had to be destroyed to eradicate BSE and the chances of humans catching CJD.
 

Parasite

Malarial parasites of the genus Plasmodium, which are carried by Anopheles mosquitoes, have probably been responsible for half of all human deaths (excluding wars and accidents) since the Stone Age.

Most Successful Parasitic Worm In Humans

Inhabiting the small intestine and measuring up to 45 cm (1ft 6 in) in length, the large roundworm (Ascaris lumbricoides ) infects approximately 25% of the human population. Victims are usually infected with up to 20 worms. The simultaneous migration of large quantities of Ascaris larvae through the lungs can cause severe haemorrhagic pneumonia. This roundworm is the most ubiquitous parasite of humans with an estimated 1 billion people infected worldwide. Each female worm produces approximately 200,000 eggs per day with an estimated total of 27 million during its life span. The eggs are highly resistant to all kinds of environmental conditions, which contributes to its widespread distribution.
 

The cold is caused by a group of rhinoviruses, of which there are at least 180 types. The condition is almost universal, except for those living in small isolated communities or in the frozen wastes of Antarctica.

Deadliest E.Coli Outbreak

Twenty people died, and 500 became ill, after consuming meat contaminated by Escherichia Coli O157-H7. The meat was bought from a butcher’s shop in Wishaw, Scotland, in 1998. Escherichia Coli O157-H7 is a dangerous strain of a normally harmless bacterium, which is believed to be transmitted by food. Reports from the United States Centers for Disease Control (CDC) estimate that 73,000 cases of infection and 61 deaths occur in America each year from Escherichia coli 0157-H7. Infection can lead to diarrhea and kidney failure. Most illness has been associated with eating undercooked, contaminated ground beef.
 

Smallest parasite

the smallest parasitic animals are various unicellular, protozoan parasites, some of which are only a few micrometers long.  The smallest of these is Pneumocystis carinii, which is only about 0.02 in long. It inhabits the lungs and causes pneumonia in humans