Pontiac fever is known to have a short incubation period of 1 to 3 days. No fatalities have been reported and cases resolve spontaneously without treatment. It is often not reported. Age, gender, and smoking do not seem to be risk factors. Pontiac fever seems to affect young people in the age medians of 29, 30, and 32. Pathogenesis of the Pontiac fever is poorly known.

Pontiac fever does not spread from person to person. It is acquired through aersolization of water droplets and/or potting soil containing "Legionella" bacteria.

The fatality rate of Legionnaires' disease has ranged from 5% to 30% during various outbreaks and approaches 50% for nosocomial infections, especially when treatment with antibiotics is delayed. Hospital-acquired "Legionella" pneumonia has a fatality rate of 28%, and the principal source of infection in such cases is the drinking-water distribution system.

The pathogenic agent is found everywhere except New Zealand. The bacterium is extremely sustainable and virulent: a single organism is able to cause an infection. The common source of infection is inhalation of contaminated dust, contact with contaminated milk, meat, or wool, and particularly birthing products. Ticks can transfer the pathogenic agent to other animals. Transfer between humans seems extremely rare and has so far been described in very few cases.

Some studies have shown more men to be affected than women, which may be attributed to different employment rates in typical professions.

“At risk” occupations include:

- Veterinary personnel

- Stockyard workers

- Farmers

- Sheep shearers

- Animal transporters

- Laboratory workers handling potentially infected veterinary samples or visiting abattoirs

- People who cull and process kangaroos

- Hide (tannery) workers

They are usually spread by eating or drinking food or water contaminated with the feces of an infected person. They may occur when a person who prepares food is infected. Risk factors include poor sanitation as is found among poor crowded populations. Occasionally they may be transmitted by sex. Humans are the only animal infected.

Although the risk of Legionnaires' disease being spread by large-scale water systems cannot be eliminated, it can be greatly reduced by writing and enforcing a highly detailed, systematic water safety plan appropriate for the specific type of facility involved (office building, hospital, hotel, spa, cruise ship, etc.) Some of the elements that such a plan may include are the following:

- Keeping water temperature either above or below the range in which the "Legionella" bacterium thrives.

- Preventing stagnation, for example by removing from a network of pipes any sections that have no outlet (dead ends). Where stagnation is unavoidable, for example when a wing of a hotel is closed for the off-season, systems must be thoroughly disinfected just prior to resuming normal operation.

- Preventing the buildup of biofilm, for example by not using (or by replacing) construction materials that encourage its development, and by reducing the quantity of nutrients for bacterial growth that enter the system.

- Periodic disinfection of the system, by high heat or a chemical biocide, and the use of chlorination where appropriate.

- System design (or renovation) that reduces the production of aerosols and reduces human exposure to them, for example by directing them well away from building air intakes.

An effective water safety plan will also cover such matters as training, record-keeping, communication among staff, contingency plans and management responsibilities. The format and content of the plan may be prescribed by public health laws or regulations. There is tentative evidence for the treatment of the water with copper-silver ionization or ultraviolet light.

Paratyphoid B is more frequent in Europe. It can present as a typhoid-like illness, as a severe gastroenteritis or with features of both. Herpes labialis, rare in true typhoid fever, is frequently seen in paratyphoid B. Diagnosis is with isolation of the agent in blood or stool and demonstration of antibodies antiBH in the Widal test. The disease responds well to chloramphenicol or co-trimoxazole.

A drug-resistant strain of scarlet fever, resistant to macrolide antibiotics such as erythromycin, but retaining drug-sensitivity to beta-lactam antibiotics such as penicillin, emerged in Hong Kong in 2011, accounting for at least two deaths in that city—the first such in over a decade. About 60% of circulating strains of the group A "Streptococcus" which cause scarlet fever in Hong Kong are resistant to macrolide antibiotics, says Professor Kwok-yung Yuen, head of Hong Kong University's microbiology department. Previously, observed resistance rates had been 10–30%; the increase is likely the result of overuse of macrolide antibiotics in recent years.

Strep throat is caused by group A beta-hemolytic streptococcus (GAS or S. pyogenes). Other bacteria such as non–group A beta-hemolytic streptococci and fusobacterium may also cause pharyngitis. It is spread by direct, close contact with an infected person; thus crowding, as may be found in the military and schools, increases the rate of transmission. Dried bacteria in dust are not infectious, although moist bacteria on toothbrushes or similar items can persist for up to fifteen days. Contaminated food can result in outbreaks, but this is rare. Of children with no signs or symptoms, 12% carry GAS in their pharynx, and, after treatment, approximately 15% of those remain positive, and are true "carriers".

Occupations at risk include veterinarians, slaughterhouse workers, farmers, sailors on rivers, sewer maintenance workers, waste disposal facility workers, and people who work on derelict buildings. Slaughterhouse workers can contract the disease through contact with infected blood or body fluids. Rowers, kayakers and canoeists also sometimes contract the disease. It was once mostly work-related but is now often also related to adventure tourism and recreational activities.

It is estimated that seven to ten million people are infected by leptospirosis annually. One million cases of severe leptospirosis occur annually, with 58,900 deaths. Annual rates of infection vary from 0.02 per 100,000 in temperate climates to 10 to 100 per 100,000 in tropical climates. This leads to a lower number of registered cases than likely exists.

The number of new cases of leptospirosis is difficult to estimate since many cases of the disease go unreported. There are many reasons for this, but the biggest issue is separating the disease from other similar conditions. Laboratory testing is lacking in many areas.

In context of global epidemiology, the socioeconomic status of many of the world’s population is closely tied to malnutrition; subsequent lack of micronutrients may lead to increased risk of infection and death due to leptospirosis infection. Micronutrients such as iron, calcium, and magnesium represent important areas of future research.

Outbreaks that occurred after the 1940's have happened mostly in the late summer seasons, which happens to be the driest part of the year. The people at the highest risk for leptospirosis are young people whose age ranges from 5-16 years old, and can also range to young adults.

The amount of cases increase during the rainy season in the tropics and during the late summer or early fall in Western countries. This happens because leptospires survive best in fresh water, damp alkaline soil, vegetation, and mud with temperatures higher that 22° C. This also leads to increased risk of exposure to populations during flood conditions, and leptospire concentrations to peak in isolated pools during drought. There is no evidence of leptospirosis having any effect on sexual and age-related differences. However, a major risk factor for development of the disease is occupational exposure, a disproportionate number of working-aged males are affected. There have been reported outbreaks where more than 40% of people are younger than 15. “Active surveillance measures have detected leptospire antibodies in as many as 30% of children in some urban American populations.” Potential reasons for such cases include children playing with suspected vectors such as dogs or indiscriminate contact with water.

Protection is offered by Q-Vax, a whole-cell, inactivated vaccine developed by an Australian vaccine manufacturing company, CSL Limited. The intradermal vaccination is composed of killed "C. burnetii" organisms. Skin and blood tests should be done before vaccination to identify pre-existing immunity, because vaccinating people who already have an immunity can result in a severe local reaction. After a single dose of vaccine, protective immunity lasts for many years. Revaccination is not generally required. Annual screening is typically recommended.

In 2001, Australia introduced a national Q fever vaccination program for people working in “at risk” occupations. Vaccinated or previously exposed people may have their status recorded on the Australian Q Fever Register, which may be a condition of employment in the meat processing industry. An earlier killed vaccine had been developed in the Soviet Union, but its side effects prevented its licensing abroad.

Preliminary results suggest vaccination of animals may be a method of control. Published trials proved that use of a registered phase vaccine (Coxevac) on infected farms is a tool of major interest to manage or prevent early or late abortion, repeat breeding, anoestrus, silent oestrus, metritis, and decreases in milk yield when "C. burnetii" is the major cause of these problems.

The symptoms of strep throat usually improve within three to five days, irrespective of treatment. Treatment with antibiotics reduces the risk of complications and transmission; children may return to school 24 hours after antibiotics are administered. The risk of complications in adults is low. In children, acute rheumatic fever is rare in most of the developed world. It is, however, the leading cause of acquired heart disease in India, sub-Saharan Africa and some parts of Australia.

Complications arising from streptococcal throat infections include:

- Acute rheumatic fever

- Scarlet fever

- Streptococcal toxic shock syndrome

- Glomerulonephritis

- PANDAS syndrome

- Peritonsillar abscess

- Cervical lymphadenitis

- Mastoiditis

The economic cost of the disease in the United States in children is approximately $350 million annually.

Currently, no vaccine against relapsing fever is available, but research continues. Developing a vaccine is very difficult because the spirochetes avoid the immune response of the infected person (or animal) through antigenic variation. Essentially, the pathogen stays one step ahead of antibodies by changing its surface proteins. These surface proteins, lipoproteins called variable major proteins, have only 30–70% of their amino acid sequences in common, which is sufficient to create a new antigenic "identity" for the organism. Antibodies in the blood that are binding to and clearing spirochetes expressing the old proteins do not recognize spirochetes expressing the new ones. Antigenic variation is common among pathogenic organisms. These include the agents of malaria, gonorrhea, and sleeping sickness. Important questions about antigenic variation are also relevant for such research areas as developing a vaccine against HIV and predicting the next influenza pandemic.

Only 8% of infected horses have this form of pigeon fever, however, it has a 30-40% fatality rate. Organs that are commonly affected are the liver, spleen, and lungs. For a successful recovery, long-term antimicrobial therapy is essential.

Spread of strep throat occurs by close contact, via respiratory droplets (for example, saliva or nasal discharge). A person in close contact with another person infected with Group A streptococcal pharyngitis has a 35% chance of becoming infected. One in ten children who are infected with Group A streptococcal pharyngitis will develop scarlet fever.

There are several populations that have a higher risk for contracting coccidioidomycosis and developing the advanced disseminated version of the disease. Populations with exposure to the airborne arthroconidia working in agriculture and construction have a higher risk. Outbreaks have also been linked to earthquakes, windstorms and military training exercises where the ground is disturbed. Historically an infection is more likely to occur in males than females, although this could be attributed to occupation rather than gender specific. Women who are pregnant and immediately postpartum are at a high risk of infection and dissemination. There is also an association between stage of pregnancy and severity of the disease, with third trimester women being more likely to develop dissemination. Presumably this is related to highly elevated hormonal levels, which stimulate growth and maturation of spherules and subsequent release of endospores. Certain ethnic populations are more susceptible to disseminated coccioidomycosis. The risk of dissemination is 175 times greater in Filipinos and 10 times greater in African Americans than non-Hispanic whites. Individuals with a weakened immune system are also more susceptible to the disease. In particular, individuals with HIV and diseases that impair T-cell function. Individuals with pre-existing conditions such as diabetes are also at a higher risk. Age also affects the severity of the disease, with more than one third of deaths being in the 65-84 age group.

The bacterium that causes typhoid fever may be spread through poor hygiene habits and public sanitation conditions, and sometimes also by flying insects feeding on feces. Public education campaigns encouraging people to wash their hands after defecating and before handling food are an important component in controlling spread of the disease. According to statistics from the United States Centers for Disease Control and Prevention (CDC), the chlorination of drinking water has led to dramatic decreases in the transmission of typhoid fever in the United States.

About 33 million people are affected by rheumatic heart disease with an additional 47 million having asymptomatic damage to their heart valves. As of 2010 globally it resulted in 345,000 deaths, down from 463,000 in 1990.

In Western countries, rheumatic fever has become fairly rare since the 1960s, probably due to the widespread use of antibiotics to treat streptococcus infections. While it has been far less common in the United States since the beginning of the 20th century, there have been a few outbreaks since the 1980s. Although the disease seldom occurs, it is serious and has a case-fatality rate of 2–5%.

Rheumatic fever primarily affects children between ages 5 and 17 years and occurs approximately 20 days after strep throat. In up to a third of cases, the underlying strep infection may not have caused any symptoms.

The rate of development of rheumatic fever in individuals with untreated strep infection is estimated to be 3%. The incidence of recurrence with a subsequent untreated infection is substantially greater (about 50%). The rate of development is far lower in individuals who have received antibiotic treatment. Persons who have suffered a case of rheumatic fever have a tendency to develop flare-ups with repeated strep infections.

The recurrence of rheumatic fever is relatively common in the absence of maintenance of low dose antibiotics, especially during the first three to five years after the first episode. Recurrent bouts of rheumatic fever can lead to valvular heart disease. Heart complications may be long-term and severe, particularly if valves are involved. In countries in Southeast-Asia, sub-saharan Africa, and Oceania, the percentage of people with rheumatic heart disease detected by listening to the heart was 2.9 per 1000 children and by echocardiography it was 12.9 per 1000 children.

When proper treatment is provided for patients with rat-bite fever, the prognosis is positive. Without treatment, the infection usually resolves on its own, although it may take up to a year to do so. A particular strain of rat-bite fever in the United States can progress and cause serious complications that can be potentially fatal. Before antibiotics were used, many cases resulted in death. If left untreated, streptobacillary rat-bite fever can result in infection in the lining of the heart, covering over the spinal cord and brain, or in the lungs. Any tissue or organ throughout the body may develop an abscess.

While obviously preventable by staying away from rodents, otherwise hands and face should be washed after contact and any scratches both cleaned and antiseptics applied. The effect of chemoprophylaxis following rodent bites or scratches on the disease is unknown. No vaccines are available for these diseases.

Improved conditions to minimize rodent contact with humans are the best preventive measures. Animal handlers, laboratory workers, and sanitation and sewer workers must take special precautions against exposure. Wild rodents, dead or alive, should not be touched and pets must not be allowed to ingest rodents.

Those living in the inner cities where overcrowding and poor sanitation cause rodent problems are at risk from the disease. Half of all cases reported are children under 12 living in these conditions.

The disease can occur in horses of any age, breed or gender. In the US, it occurs throughout the country and at any time of year. The disease was traditionally thought to occur mainly in dry, arid regions, but from at least 2005, its range has been increasing into areas where it was not previously seen, such as the Midwestern US, and Western Canada. Environmental risk factors include over 7 days of a weekly average land surface temperatures above 35 °C, and drier soils; these factors were implicated in an outbreak in Kansas in 2012.

Haverhill fever (or epidemic arthritic erythema) is a form of "rat-bite fever" caused by the bacterium "Streptobacillus moniliformis", an organism common in rats and mice. Symptoms begin to appear two to ten days after a rat bite injury. The illness resembles a severe influenza, with a moderate fever (38-40 °C, or 101-104 °F), chills, joint pain, and a diffuse red rash, located mostly on the hands and feet. The causative organism can be isolated by blood culture, and penicillin is the most common treatment. Treatment is usually quite successful, although the body can clear the infection by itself in most cases. Complications are rare, but can include endocarditis and meningitis.

Despite its name, it can present without being bitten by a rat.

The disease was recognized from an outbreak which occurred in Haverhill, Massachusetts in January, 1926. The organism "S. moniliformis" was isolated from the patients. Epidemiology implicated infection via consumption of milk from one particular dairy.

Preventing Valley fever is challenging because it is difficult to avoid breathing in the fungus should it be present, however, the public health effect of the disease is essential to understand in areas where the fungus is endemic. Enhancing surveillance of Coccidiodomycosis is key to preparedness in the medical field in addition to improving diagnostics for early infections. Currently there are no completely effective preventive measures available for people who live or travel through Valley Fever -endemic areas. Recommended preventive measures include avoiding airborne dust or dirt, but this does not guarantee protection against infection. People in certain occupations may be advised to wear face masks. The use of air filtration indoors is also helpful, in addition to keeping skin injuries clean and covered to avoid skin infection.

In 1998-2011, there were 111,117 cases of coccidioidomycosis in the U.S. that were logged into the National Notifiable Diseases Surveillance System (NNDSS). Since many U.S. states do not require reporting of coccidioidomycosis, the actual numbers can be higher. The United States' Centers for Disease Control and Prevention (CDC) called the disease a "silent epidemic" and acknowledged that there is no proven anticoccidioidal vaccine available. Studies done in the past show that the cost benefit of a vaccine is most notable among infants, teens, and immigrant adults, with negative cost-benefit results among older age groups.

Raising both surveillance and awareness of the disease while medical researchers are developing a human vaccine can positively contribute towards prevention efforts. Research demonstrates that patients from endemic areas who are aware of the disease are most likely to request diagnostic testing for coccidioidomycosis. Presently, Meridian Bioscience manufactures the so-called "EIA test" to diagnose the Valley fever, which however is known for producing a fair quantity of false positives. Currently, recommended prevention measures can include type-of-exposure-based respirator protection for persons engaged in agriculture, construction and others working outdoors in endemic areas. Dust control measures such as planting grass and wetting the soil, and also limiting exposure to dust storms are advisable for residential areas in endemic regions.

As of 2017 there is no commercially available vaccine. A vaccine has been in development for scrub typhus known as the scrub typhus vaccine.