Individuals at higher risk are often prescribed prophylactic medication to prevent an infection from occurring. A patient's risk level for developing an opportunistic infection is approximated using the patient's CD4 T-cell count and sometimes other markers of susceptibility. Common prophylaxis treatments include the following:

Since opportunistic infections can cause severe disease, much emphasis is placed on measures to prevent infection. Such a strategy usually includes restoration of the immune system as soon as possible, avoiding exposures to infectious agents, and using antimicrobial medications ("prophylactic medications") directed against specific infections.

Most household disinfectants will inactivate FHV-1. The virus can survive up to 18 hours in a damp environment, but less in a dry environment and only shortly as an aerosol.

Bats recovering from white-nose syndrome (WNS) may be the first natural occurrence of IRIS, in a report released by the USGS. WNS is typified by a cutaneous infection of the fungus "Pseudogymnoascus destructans" during hibernation, when the immune system is naturally suppressed to conserve energy through the winter. This study suggests that bats undergoing an intense inflammation at the site of infection after a return to euthermia is a form of IRIS.

There is a vaccine for FHV-1 available (ATCvet code: , plus various combination vaccines), but although it limits or weakens the severity of the disease and may reduce viral shedding, it does not prevent infection with FVR. Studies have shown a duration of immunity of this vaccine to be at least three years. The use of serology to demonstrate circulating antibodies to FHV-1 has been shown to have a positive predictive value for indicating protection from this disease.

Fever and sickness behavior and other signs of infection are often taken to be due to them. However, they are evolved physiological and behavioral responses of the host to clear itself of the infection. Instead of incurring the costs of deploying these evolved responses to infections, the body opts to tolerate an infection as an alternative to seeking to control or remove the infecting pathogen.

Subclinical infections are important since they allow infections to spread from a reserve of carriers. They also can cause clinical problems unrelated to the direct issue of infection. For example, in the case of urinary tract infections in women, this infection may cause preterm delivery if the person becomes pregnant without proper treatment.

An individual may only develop signs of an infection after a period of subclinical infection, a duration that is called the incubation period. This is the case, for example, for subclinical sexually transmitted diseases such as AIDS and genital warts. Individuals with such subclinical infections, and those that never develop overt illness, creates a reserve of individuals that can transmit an infectious agent to infect other individuals. Because such cases of infections do not come to clinical attention, health statistics can often fail to measure the true prevalence of an infection in a population, and this prevents the accurate modeling of its infectious transmission.

One strategy for the prevention of infection transmission between cats and people is to better educate people on the behaviour that puts them at risk for becoming infected.

Those at the highest risk of contracting a disease from a cat are those with behaviors that include: being licked, sharing food, sharing kithchen utensils, kissing, and sleeping with a cat. The very young, the elderly and those who are immunocompromised increase their risk of becoming infected when sleeping with their cats (and dogs). The CDC recommends that cat owners not allow a cat to lick your face because it can result in disease transmission. If someone is licked on their face, mucous membranes or an open wound, the risk for infection is reduced if the area is immediately washed with soap and water. Maintaining the health of the animal by regular inspection for fleas and ticks, scheduling deworming medications along with veterinary exams will also reduce the risk of acquiring a feline zoonosis.

Recommendations for the prevention of ringworm transmission to people include:

- regularly vacuuming areas of the home that pets commonly visit helps to remove fur or flakes of skin

- washing the hands with soap and running water after playing with or petting your pet.

- wearing gloves and long sleeves when handling cats infected with.

- disinfect areas the pet has spent time in, including surfaces and bedding.

- the spores of this fungus can be killed with common disinfectants like chlorine bleach diluted 1:10 (1/4 cup in 1 gallon of water), benzalkonium chloride, or strong detergents.

- not handling cats with ringworm by those whose immune system is weak in any way (if you have HIV/AIDS, are undergoing cancer treatment, or are taking medications that suppress the immune system, for example).

- taking the cat to the veterinarian if ringworm infection is suspected.

SuHV1 can be used to analyze neural circuits in the central nervous system (CNS). For this purpose the attenuated (less virulent) Bartha SuHV1 strain is commonly used and is employed as a retrograde and anterograde transneuronal tracer. In the retrograde direction, SuHV1-Bartha is transported to a neuronal cell body via its axon, where it is replicated and dispersed throughout the cytoplasm and the dendritic tree. SuHV1-Bartha released at the synapse is able to cross the synapse to infect the axon terminals of synaptically connected neurons, thereby propagating the virus; however, the extent to which non-synaptic transneuronal transport may also occur is uncertain. Using temporal studies and/or genetically engineered strains of SuHV1-Bartha, second, third, and higher order neurons may be identified in the neural network of interest.

Although no specific treatment for acute infection with SuHV1 is available, vaccination can alleviate clinical signs in pigs of certain ages. Typically, mass vaccination of all pigs on the farm with a modified live virus vaccine is recommended. Intranasal vaccination of sows and neonatal piglets one to seven days old, followed by intramuscular (IM) vaccination of all other swine on the premises, helps reduce viral shedding and improve survival. The modified live virus replicates at the site of injection and in regional lymph nodes. Vaccine virus is shed in such low levels, mucous transmission to other animals is minimal. In gene-deleted vaccines, the thymidine kinase gene has also been deleted; thus, the virus cannot infect and replicate in neurons. Breeding herds are recommended to be vaccinated quarterly, and finisher pigs should be vaccinated after levels of maternal antibody decrease. Regular vaccination results in excellent control of the disease. Concurrent antibiotic therapy via feed and IM injection is recommended for controlling secondary bacterial pathogens.

Some disease-carrying arthropods use cats as a vector, or carrier. Fleas and ticks can carry pathogenic organisms that infect a person with Lyme disease, tick borne encephalitis, and Rocky mountain spotted fever

Treatment is often only recommended for people with serious health problems, such as people with HIV whose CD4 counts are under 200 cells/mm, because the disease is most serious when one's immune system is weak. Trimethoprim/sulfamethoxazole is the drug of choice to prevent toxoplasmosis, but not for treating active disease.

A new study (May 2012) shows a promising new way to treat the active and latent form of this disease using two endochin-like quinolones.

In people with latent toxoplasmosis, the cysts are immune to these treatments, as the antibiotics do not reach the bradyzoites in sufficient concentration.

The medications prescribed for latent toxoplasmosis are:

- Atovaquone — an antibiotic that has been used to kill "Toxoplasma" cysts inside AIDS patients

- Clindamycin — an antibiotic that, in combination with atovaquone, seemed to optimally kill cysts in mice

The preventative measure of keeping cats inside in areas with high infection rates can prevent infection. Approved tick treatments for cats can be used but have been shown not to fully prevent tick bites.

The most often used treatments for cytauxzoonosis are imidocarb dipropionate and a combination of atovaquone and azithromycin. Although imidocarb has been used for years, it is not particularly effective. In a large study, only 25% of cats treated with this drug and supportive care survived. 60% of sick cats treated with supportive care and the combination of the anti-malarial drug atovaquone and the antibiotic azithromycin survived infection.

Quick referral to a veterinarian equipped to treat the disease may be beneficial. All infected cats require supportive care, including careful fluids, nutritional support, treatment for complications, and often blood transfusion.

Cats that survive the infection should be kept indoors as they can be persistent carriers after surviving infection and might indirectly infect other cats after being themselves bitten by a vector tick.

Cat-scratch disease can be primarily prevented by taking flea control measures and washing hands after handling a cat or cat feces; since cats are mostly exposed to fleas when they are outside, keeping cats inside can prevent infestation.

Doxycycline is the drug of choice, but azithromycin is also used as a five-day course rather than a single dose that would be used to treat "Chlamydia" infection; streptomycin is an alternative, but is less popular because it must be injected. Penicillins are ineffective — "U. urealyticum" does not have a cell wall, which is the drug's main target.

To reduce neonatal infection, routine screening of pregnant women for HIV, hepatitis B, syphilis, and rubella susceptibility is required in the UK.

Treatment with an vaginal antibiotic wash prior to birth does not prevent infection with group B streptococcus bacteria. Breast milk protects against necrotizing enterocolitis.

Because GBS bacteria can colonize the lower reproductive tract of 30% of women, typically pregnant women are tested for this pathogen from 35 to 37 weeks of pregnancy. Before delivery treatment of the mother with antibiotics reduces the rate of neonatal infection. Prevention of the infection of the baby is done by treating the mother with penicillin. Since the adoption of this prophylatic treatment, infant mortality from GBS infection has decreased by 80%.

Mothers with symptomatic HSV and who are treated with antiviral prophylaxis are less prone to have an active, symptomatic case at the time of birth and it may be able to reduce the risk of passing on HSV during birth. Cesarean delivery reduces the risk of infection of the infant.

The mainstay of eradication is the identification and removal of persistently infected animals. Re-infection is then prevented by vaccination and high levels of biosecurity, supported by continuing surveillance. PIs act as viral reservoirs and are the principal source of viral infection but transiently infected animals and contaminated fomites also play a significant role in transmission.

Leading the way in BVD eradication, almost 20 years ago, were the Scandinavian countries. Despite different conditions at the start of the projects in terms of legal support, and regardless of initial prevalence of herds with PI animals, it took all countries approximately 10 years to reach their final stages.

Once proven that BVD eradication could be achieved in a cost efficient way, a number of regional programmes followed in Europe, some of which have developed into national schemes.

Vaccination is an essential part of both control and eradication. While BVD virus is still circulating within the national herd, breeding cattle are at risk of producing PI neonates and the economic consequences of BVD are still relevant. Once eradication has been achieved, unvaccinated animals will represent a naïve and susceptible herd. Infection from imported animals or contaminated fomites brought into the farm, or via transiently infected in-contacts will have devastating consequences.

Most healthy people clear the infection without treatment, but in 5 to 14 percent of individuals, the organisms disseminate and infect the liver, spleen, eye, or central nervous system. Although some experts recommend not treating typical CSD in immunocompetent patients with mild to moderate illness, treatment of all patients with antimicrobial agents (Grade 2B) is suggested due to the probability of disseminated disease. The preferred antibiotic for treatment is azithromycin since this agent is the only one studied in a randomized controlled study.

Azithromycin is preferentially used in pregnancy to avoid the teratogenic side effects of doxycycline. However, doxycycline is preferred to treat "B. henselae" infections with optic neuritis due to its ability to adequately penetrate the tissues of the eye and central nervous system.

The suppression of CD4 T cells by HIV (or by immunosuppressive drugs) causes a decrease in the body's normal response to certain infections. Not only does this make it more difficult to fight the infection, it may mean that a level of infection that would normally produce symptoms is instead undetected (subclinical infection). If the CD4 count rapidly increases (due to effective treatment of HIV, or removal of other causes of immunosuppression), a sudden increase in the inflammatory response produces nonspecific symptoms such as fever, and in some cases a worsening of damage to the infected tissue.

There are two common IRIS scenarios. The first is the “unmasking” of an opportunistic infection. The second is the “paradoxical” symptomatic relapse of a prior infection despite microbiologic treatment success. Often in paradoxical IRIS, microbiologic cultures are sterile. In either scenario, there is hypothesized reconstitution of antigen-specific T cell-mediated immunity with activation of the immune system following HIV therapy against persisting antigen, whether present as intact organisms, dead organisms, or debris.

Though these symptoms can be dangerous, they also indicate that the body may now have a better chance to defeat the infection. The best treatment for this condition is unknown. In paradoxical IRIS reactions, the events will usually spontaneously get better with time without any additional therapy. In unmasking IRIS, the most common treatment is to administer antibiotic or antiviral drugs against the infectious organism. In some severe cases, anti-inflammatory medications, such as corticosteroids are needed to suppress inflammation until the infection has been eliminated.

Infections most commonly associated with IRIS include "Mycobacterium tuberculosis" and cryptococcal meningitis. Persons living with AIDS are more at risk for IRIS if they are starting for the first time, or if they have recently been treated for an opportunistic infection (OI). It is generally advised that when patients have low initial CD4 T cell count and opportunistic infection at the time of their HIV diagnosis, they receive treatment to control the opportunistic infections before HAART is initiated approximately two weeks later. This is true for most OIs, except for OIs involving the central nervous system.

Modern vaccination programmes aim not only to provide a high level of protection from clinical disease for the dam, but, crucially, to protect against viraemia and prevent the production of PIs. While the immune mechanisms involved are the same, the level of immune protection required for foetal protection is much higher than for prevention of clinical disease.

While challenge studies indicate that killed, as well as live, vaccines prevent foetal infection under experimental conditions, the efficacy of vaccines under field conditions has been questioned. The birth of PI calves into vaccinated herds suggests that killed vaccines do not stand up to the challenge presented by the viral load excreted by a PI in the field.

Experimental infection in immunocompetent and immunocompromised mice has produced intestinal inflammation, altered bowel habits, lethargy and death. Chronic diarrhea has been reported in non-human higher primates.

Each type of vertically transmitted infection has a different prognosis. The stage of the pregnancy at the time of infection also can change the effect on the newborn.

Some vertically transmitted infections, such as toxoplasmosis and syphilis, can be effectively treated with antibiotics if the mother is diagnosed early in her pregnancy. Many viral vertically transmitted infections have no effective treatment, but some, notably rubella and varicella-zoster, can be prevented by vaccinating the mother prior to pregnancy.

If the mother has active herpes simplex (as may be suggested by a pap test), delivery by Caesarean section can prevent the newborn from contact, and consequent infection, with this virus.

IgG antibody may play crucial role in prevention of intrauterine infections and extensive research is going on for developing IgG-based therapies for treatment and vaccination.

Neonatal infection treatment is typically started before the diagnosis of the cause can be confirmed.

Neonatal infection can be prophylactically treated with antibiotics. Maternal treatment with antibiotics is primarily used to protect against group B streptococcus.

Women with a history of HSV, can be treated with antiviral drugs to prevent symptomatic lesions and viral shedding that could infect the infant at birth. The antiviral medications used include acyclovir, penciclovir, valacyclovir, and famciclovir. Only very small amounts of the drug can be detected in the fetus. There are no increases in drug-related abnormalities in the infant that could be attributed to acyclovir. Long-term effects of antiviral medications have not been evaluated for their effects after growth and development of the child occurs. Neutropenia can be a complication of acyclovir treatment of neonatal HSV infection, but is usually transient. Treatment with immunoglobulin therapy has not been proven to be effective.