What is the difference between localized and systemic infections?
Localized is where the infection is confined to a local area of the body - systemic is where the infection has spread throughtout the body. systemic infections are very serious.
What are some examples of systemic infections?
Bacterial infections with systemic spread usually result in sepsis - the life-threatening inflammatory (over-)reaction to (mainly) bacterial substances entering the bloodstream.For viruses, generally, if there is a rash, there is a systemic infection. Measles, chickenpox etc. Viral infections may be systemic without causing a rash though.Malaria is the prime example of a parasitical systemic infection. The parasites infect red blood cells and make them burst, causing a strong systemic inflammatory response.Fungi can also cause systemic infections, primarily in people with a weakened immune system. Examples are invasive aspergillosis (caused by a mold) and systemic candidiasis (caused by a yeast).
Can you have a bacterial/viral infection without having a fever?
To answer your question: sure. Sometimes infections provoke no fever, even severe ones. The current definition of sepsis (a more severe infection) includes 4 signs, and temperature changes is only one. You only have to have 2 of the 4 and an infection to meet the definition of sepsis. But more importantly, the temperature one is that you have either a fever OR a low temperature. Common reasons for no temperature with infection include a mild, not systemically serious infection; advanced age; lower starting point (normal temperature below the average), fever suppressing medications from tylenol or ibuprofen to immunosuppressive medicines; serious infections which can cause low temperatures; some low pathogenicity infections (I recall a patient who had bacteria eating through his heart valves, going on long enough he lost weight and his diabetes improved from it--but no fever at all. It was enterococcus, which just doesn't cause as acute a syndrome as many other bacteria). Beyond that, doctors shouldn't just fire a bunch of antibiotics at swollen glands without a clue as to what's happening. There are many causes of swollen glands, and randomly choosing an antibiotic isn't going to fix lymphoma, or tuberculosis, or a viral infection, or run unusual bacterial infection. In a stable patient, diagnosis comes before treatment.
What is the difference between contact and systemic fungicides?
Contact fungicides, like copper, mancozeb and chlorthalonil act on the outside of the plant mostly by interfering with spore germination. They can also have an effect on the growth of hyphae. They won't stop an infection though. Systemic fungicides act within the plant after being taken up in the tissue and translocated through the plant. These fungicides can kill a fungus after infection during incubation (curative control) or with symptoms already visible (eradicant control). Examples are triazoles, SDHI's and QoI’s. Contact fungicides are mostly multi site inhibitors while systemic fungicides single site inhibitors. The latter is more prone to resistance build up of the target fungal population.
What are the differences between a local disease and a focal disease?
Local disease is an infection limited to one part of the body. An example of localized infection is common cold, which affects only the nose and throat, as opposed to a systematic infection, like flu, which affects pretty much all your body. Focal disease is a term usually used for a specific disease like focal glomerulonephritis (a type of kidney inflammation), in which only some parts of the kidney glomeruli are affected, as opposed to diffuse glomerulonephritis, in which the entire glomerulus is affected. Focal pneumonia affects only one lung lobe (lobar pneumonia).In summary: "Localized" vs "systemic" is used from the perspective of the whole body. "Focal" vs "diffuse" is used from the perspective of a single organ.