New diseases in 21st century.

Public health measures indeed have improved a lot in the past sevaral hundred years. The total eradication of smallpox and the near eradication of polio fostered an illusion that that modern medical science and public health had the tools to protect society and to eradicate diseases one by one. But new diseases like severe acute respiratory syndrome(SARS), avian flu and swine flu proved that our society is still vulnerable, particularly to respiratory infections in the industrial world, transmitted by air or droplets. They're true diseases of globalization and modernity, that thrive on high population density and modern means of high-speed communication.

New Diseases Gallery

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SARS coronavirus
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A chest X-ray of a patient with SARS
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Areas of the world affected by SARS in 2002–2003
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Avian flu H5N1 viruses
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Swine fle H1N1 viruses
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Main symptoms of swine flu in humans

SARS coronavirus
A chest X-ray of a patient with SARS
Areas of the world affected by SARS in 2002–2003
Avian flu H5N1 viruses
Swine fle H1N1 viruses
Main symptoms of swine flu in humans

SARS

Between November 2002 and July 2003, an outbreak of SARS in southern China caused an eventual 8,098 cases, resulting in 774 deaths reported in 37 countries, with the majority of cases in China and Hong Kong. No cases of SARS have been reported worldwide since 2004.

Pathogen
SARS coronavirus.
Symptoms
After 4-6 days of incubation period, SARS begins with a high fever (temperature greater than 100.4°F). Other symptoms may include headache, an overall feeling of discomfort, and body aches. Some people also have mild respiratory symptoms at the outset. About 10 percent to 20 percent of patients have diarrhea. After 2 to 7 days, SARS patients may develop a dry cough. Most patients develop pneumonia.
Transmission
The main way that SARS seems to spread is by close person-to-person contact. The virus that causes SARS is thought to be transmitted most readily by respiratory droplets (droplet spread) produced when an infected person coughs or sneezes. The virus also can spread when a person touches a surface or object contaminated with infectious droplets and then toucheshis or her mouth, nose, or eyes.

Avian Flu

Avian flu is accurately a variety of influenza caused by viruses adapted to birds. There are three types of influenza viruses (A, B, and C), but avian flu, for most purposes, refers to the influenza A virus. Between early 2013 and early 2017, 916 lab-confirmed human cases of H7N9 were reported to the World Health Organization.

Pathogen
Normally H5N1, H7N3, H7N7, H7N9, and H9N2.
Symptoms
Symptoms have ranged from mild to severe and included conjunctivitis, influenza-like illness (e.g., fever, cough, sore throat, muscle aches) sometimes accompanied by nausea, abdominal pain, diarrhea, and vomiting, severe respiratory illness (e.g., shortness of breath, difficulty breathing, pneumonia, acute respiratory distress, viral pneumonia, respiratory failure), neurologic changes (altered mental status, seizures), and the involvement of other organ systems.
Transmission
Infected birds shed avian influenza virus in their saliva, mucous and feces. Human infections with bird flu viruses can happen when enough virus gets into a person’s eyes, nose or mouth, or is inhaled. This can happen when virus is in the air (in droplets or possibly dust) and a person breathes it in, or when a person touches something that has virus on it then touches their mouth, eyes or nose. However, some infections have been identified where direct contact was not known to have occurred.

Swine Flu

Swine flu is an infection caused by any one of several types of swine influenza viruses. The Swine flu was initially seen in humans in Mexico in 2009, where the strain of the particular virus was a mixture from 3 types of strains.

Pathogen
Influenza C and the subtypes of influenza A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.
Symptoms
People who have been infected with swine flu have had symptoms similar to the symptoms of regular human seasonal influenza. These include fever, lethargy, lack of appetite and coughing. Some people also have reported runny nose, sore throat, eye irritation, nausea, vomiting and diarrhea.
Transmission
Influenza viruses can be directly transmitted from pigs to people and from people to pigs. These infections have most commonly been reported after close proximity to infected pigs, such as in pig barns and livestock exhibits housing pigs at fairs. Infected pig cough or sneeze and droplets with influenza virus in them can spread through the air. If these droplets land in your nose or mouth, or are inhaled, you can be infected. There also is some evidence that you might get infected by touching a surface with virus on it and then touching your mouth or nose. A third way to possibly get infected is to inhale droplets or dust containing influenza virus.