Sixty percent of mothers of preterm infants are infected with cytomegalovirus (CMV). Infection is asymptomatic in most instances but 9% to 12% of postnatally infected low birth weight, preterm infants have severe, sepsis-like infection. CMV infection duration can be long and result in pneumonitis in association with fibrosis. CMV infection in infants has an unexpected effect on the white blood cells of the immune system causing them to prematurely age. This leads to a reduced immune response similar to that found in the elderly.

Human immunodeficiency virus type I (HIV) infection can occur during labor and delivery, in utero through mother-to-child transmission or postnatally by way of breastfeeding. Transmission can occur during pregnancy, delivery or breastfeeding. Most transmission occurs during delivery. In women with low detectable levels of the virus, the incidence of transmission is lower. Transmission risk can be reduced by:

- providing antiretroviral therapy during pregnancy and immediately after birth

- delivery by caesarean section

- not breastfeeding

- antiretroviral prophylaxis in infants born to mothers with HIV.

A low number of women whose HIV status are unknown until after the birth, do not benefit from interventions that could help lower the risk of mother-to-child HIV transmission.

Most healthy people working with infants and children face no special risk from CMV infection. However, for women of child-bearing age who previously have not been infected with CMV, there is a potential risk to the developing unborn child (the risk is described above in the Pregnancy section). Contact with children who are in day care, where CMV infection is commonly transmitted among young children (particularly toddlers), may be a source of exposure to CMV. Since CMV is transmitted through contact with infected body fluids, including urine and saliva, child care providers (meaning day care workers, special education teachers, as well as mothers) should be educated about the risks of CMV infection and the precautions they can take. Day care workers appear to be at a greater risk than hospital and other health care providers, and this may be due in part to the increased emphasis on personal hygiene in the health care setting.

Recommendations for individuals providing care for infants and children:

- Employees should be educated concerning CMV, its transmission, and hygienic practices, such as handwashing, which minimize the risk of infection.

- Susceptible nonpregnant women working with infants and children should not routinely be transferred to other work situations.

- Pregnant women working with infants and children should be informed of the risk of acquiring CMV infection and the possible effects on the unborn child.

- Routine laboratory testing for CMV antibody in female workers is not specifically recommended due to its high occurrence, but can be performed to determine their immune status.

Recommendations for pregnant women with regard to CMV infection:

- Throughout the pregnancy, practice good personal hygiene, especially handwashing with soap and water, after contact with diapers or oral secretions (particularly with a child who is in day care). Sharing of food, eating and drinking utensils, and contact with toddlers' saliva should be avoided.

- Women who develop a mononucleosis-like illness during pregnancy should be evaluated for CMV infection and counseled about the possible risks to the unborn child.

- Laboratory testing for antibody to CMV can be performed to determine if a woman has already had CMV infection.

- Recovery of CMV from the cervix or urine of women at or before the time of delivery does not warrant a cesarean section.

- The demonstrated benefits of breast-feeding outweigh the minimal risk of acquiring CMV from the breast-feeding mother.

- There is no need to either screen for CMV or exclude CMV-excreting children from schools or institutions because the virus is frequently found in many healthy children and adults.

Treatment with hyperimmune globulin in mothers with primary CMV infection has been shown to be effective in preventing congenital disease in several studies. One study did not show significant decrease in the risk of congenital cytomegalovirus infection.

If symptomatic, testing is recommended. The risk of contracting Micoplasma infection can be reduced by the following:

- Using barrier methods such as condoms

- Seeking medical attention if you are experiencing symptoms suggesting a sexually transmitted infection.

- Seeking medical attention after learning that a current or former sex partner has, or might have had a sexually transmitted infection.

- Getting a STI history from your current partner and insisting they be tested and treated before intercourse.

- Avoiding vaginal activity, particularly intercourse, after the end of a pregnancy (delivery, miscarriage, or abortion) or certain gynecological procedures, to ensure that the cervix closes.

- Abstinence

Infection in the newborn is accompanied by a strong immune response and is correlated with the need for prolonged mechanical ventilation.

Infection with "U. urealyticum" in pregnancy and birth can be complicated by chorioamnionitis, stillbirth, premature birth, and, in the perinatal period, pneumonia, bronchopulmonary dysplasia and meningitis. "U. urealyticum" has been found to be present in amniotic fluid in women who have had a premature birth with intact fetal membranes.

"U. urealyticum" has been noted as one of the infectious causes of sterile pyuria. It increases the morbidity as a cause of neonatal infections. It is associated with premature birth, preterm rupture of membranes, preterm labor, cesarean section, placental inflammation, congenital pneumonia, bacteremia, meningitis, fetal lung injury and death of infant. "Ureaplasma urealyticum" is associated with miscarriage.

Neonates, especially if preterm, are susceptible to "M. hominis" infection.

Meningoencephalitis in neonates has been described and M. hominis may be a significant causative agent of neonatal sepsis or meningitis.

"M. hominis" has been associated with chorioamnionits. "M. hominis" is associated with miscarriage.

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.

The current incidence in the United States is somewhere around 0.5% per year; overall, the incidence rate for developed world falls between 0.2–0.7%. In developing countries, the incidence of omphalitis varies from 2 to 7 for 100 live births. There does not appear to be any racial or ethnic predilection.

Like many bacterial infections, omphalitis is more common in those patients who have a weakened or deficient immune system or who are hospitalized and subject to invasive procedures. Therefore, infants who are premature, sick with other infections such as blood infection (sepsis) or pneumonia, or who have immune deficiencies are at greater risk. Infants with normal immune systems are at risk if they have had a prolonged birth, birth complicated by infection of the placenta (chorioamnionitis), or have had umbilical catheters.

Babies can also become infected by their mothers during birth. Some infectious agents may be transmitted to the embryo or fetus in the uterus, while passing through the birth canal, or even shortly after birth. The distinction is important because when transmission is primarily during or after birth, medical intervention can help prevent infections in the infant.

During birth, babies are exposed to maternal blood, body fluids, and to the maternal genital tract without the placental barrier intervening. Because of this, blood-borne microorganisms (hepatitis B, HIV), organisms associated with sexually transmitted disease (e.g., "Neisseria gonorrhoeae" and "Chlamydia trachomatis"), and normal fauna of the genitourinary tract (e.g., "Candida albicans") are among those commonly seen in infection of newborns.

The embryo and fetus have little or no immune function. They depend on the immune function of their mother. Several pathogens can cross the placenta and cause (perinatal) infection. Often, microorganisms that produce minor illness in the mother are very dangerous for the developing embryo or fetus. This can result in spontaneous abortion or major developmental disorders. For many infections, the baby is more at risk at particular stages of pregnancy. Problems related to perinatal infection are not always directly noticeable.

Research has shown a link between trichomoniasis and two serious sequelae. Data suggest that:

- Trichomoniasis is associated with increased risk of transmission and infection of HIV.

- Trichomoniasis may cause a woman to deliver a low-birth-weight or premature infant.

- The role of trichomonas infection in causing cervical cancer is unclear, although trichomonas infection may be associated with co-infection with high-risk strains of HPV.

- "T. vaginalis" infection in males has been found to cause asymptomatic urethritis and prostatitis. In the prostate, it may create chronic inflammation that may eventually lead to prostate cancer.

Immunodeficiency or immunosuppression can be caused by:

- Malnutrition

- Fatigue

- Recurrent infections

- Immunosuppressing agents for organ transplant recipients

- Advanced HIV infection

- Chemotherapy for cancer

- Genetic predisposition

- Skin damage

- Antibiotic treatment leading to disruption of the physiological microbiome, thus allowing some microorganisms to outcompete others and become pathogenic (e.g. disruption of intestinal flora may lead to "Clostridium difficile" infection

- Medical procedures

- Pregnancy

- Ageing

- Leukopenia (i.e. neutropenia and lymphocytopenia)

The lack of or the disruption of normal vaginal flora allows the proliferation of opportunistic microorganisms and will cause the opportunistic infection - bacterial vaginosis.

This depends on the age of the animal affected and the efficiency of its immune system.

Colostral protection lasts up to 5 months of age, after which it decreases to an all-time low to increase yet again at about 12 months of age.

- Prenatal infection: virus travels from infected mother to fetus via the placenta. In this case, the time of gestation determines the result of the infection.

- If the fetus is infected in the first 30 days of fetal life, death and absorption of all, or some of the fetuses may occur. In this case, some immunotolerant healthy piglets may be born.

- If the infection happens at 40 days, death and mummification may occur. Also in this case, some or all the fetuses are involved, i.e. some of the fetuses can be born healthy and immunotolerant, or else carriers of the disease.

- If the viruses crosses the placenta in the last trimester, neonatal death may occur, or the birth of healthy piglets with a protective pre-colostral immunity.

- Postnatal infection (pigs up to 1 year of age): Infection occurs oro-nasally, followed by a viremic period associated with transitory leucopenia.

- Infection in adults (over 1 year of age): These subject would have an active, protective immune system which protects them from future exposures (e.g. mating with an infected male).

Therefore, it is important to note that the virus is particularly dangerous for the sow in her first gestation, which would be at 7–8 months of age, as she would have a particularly low antibody count at this age and could easily contract the virus via copulation.

During the 1950s there were outbreaks of omphalitis that then led to anti-bacterial treatment of the umbilical cord stump as the new standard of care. It was later determined that in developed countries keeping the cord dry is sufficient, (known as "dry cord care") as recommended by the American Academy of Pediatrics. The umbilical cord dries more quickly and separates more readily when exposed to air However, each hospital/birthing center has its own recommendations for care of the umbilical cord after delivery. Some recommend not using any medicinal washes on the cord. Other popular recommendations include triple dye, betadine, bacitracin, or silver sulfadiazine. With regards to the medicinal treatments, there is little data to support any one treatment (or lack thereof) over another. However one recent review of many studies supported the use of chlorhexidine treatment as a way to reduce risk of death by 23% and risk of omphalitis by anywhere between 27-56% in community settings in underdeveloped countries. This study also found that this treatment increased the time that it would take for the umbilical stump to separate or fall off by 1.7 days. Lastly this large review also supported the notion that in hospital settings no medicinal type of cord care treatment was better at reducing infections compared to dry cord care.

There were about 58 million cases of trichomoniasis in 2013. It is more common in women (2.7%) than males (1.4%). It is the most common non-viral STI in the U.S., with an estimated 3.7 million prevalent cases and 1.1 million new cases per year. It is estimated that 3% of the general U.S. population is infected, and 7.5-32% of moderate-to-high risk (including incarcerated) populations.

The bacteria most associated with salpingitis are:

- N. gonorrhoeae

- Chlamydia trachomatis

- Mycoplasma

- Staphylococcus

- Streptococcus

However, salpingitis is usually polymicrobial, involving many kinds of organisms. Other examples of organisms involved are:

- Ureaplasma urealyticum

- Anaerobic and aerobic bacteria

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.

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.

Over one million cases of acute salpingitis are reported every year in the US, but the number of incidents is probably larger, due to incomplete and untimely reporting methods and that many cases are reported first when the illness has gone so far that it has developed chronic complications. For women age 16–25, salpingitis is the most common serious infection. It affects approximately 11% of females of reproductive age.

Salpingitis has a higher incidence among members of lower socioeconomic classes. However, this is thought of being an effect of earlier sex debut, multiple partners, and decreased ability to receive proper health care rather than any independent risk factor for salpingitis.

As an effect of an increased risk due to multiple partners, the prevalence of salpingitis is highest for people age 15–24 years. Decreased awareness of symptoms and less will to use contraceptives are also common in this group, raising the occurrence of salpingitis.

SMEDI (an acronym of stillbirth, mummification, embryonic death, and infertility) is a reproductive disease of swine caused by "Porcine parvovirus" ("PPV") and "Porcine enterovirus". The term SMEDI usually indicates "Porcine enterovirus", but it also can indicate "Porcine parvovirus", which is a more important cause of the syndrome. SMEDI also causes abortion, neonatal death, and decreased male fertility.

From an economic standpoint SMEDI is an important disease because of the loss of productivity from fetal death in affected herds. Initial infection of a herd causes the greatest effect, but losses slow over time. The disease is spread most commonly by ingestion of food and water contaminated with infected feces and occasionally through sexual contact and contact with aborted tissue. A vaccine is available (ATCvet code: ).

Chlamydia can be transmitted during vaginal, anal, or oral sex or direct contact with infected tissue such as conjunctiva. Chlamydia can also be passed from an infected mother to her baby during vaginal childbirth.

For sexually active women who are not pregnant, screening is recommended in those under 25 and others at risk of infection. Risk factors include a history of chlamydial or other sexually transmitted infection, new or multiple sexual partners, and inconsistent condom use. For pregnant women, guidelines vary: screening women with age or other risk factors is recommended by the U.S. Preventive Services Task Force (USPSTF) (which recommends screening women under 25) and the American Academy of Family Physicians (which recommends screening women aged 25 or younger). The American College of Obstetricians and Gynecologists recommends screening all at risk, while the Centers for Disease Control and Prevention recommend universal screening of pregnant women. The USPSTF acknowledges that in some communities there may be other risk factors for infection, such as ethnicity. Evidence-based recommendations for screening initiation, intervals and termination are currently not possible. For men, the USPSTF concludes evidence is currently insufficient to determine if regular screening of men for chlamydia is beneficial. They recommend regular screening of men who are at increased risk for HIV or syphilis infection.

In the United Kingdom the National Health Service (NHS) aims to:

1. Prevent and control chlamydia infection through early detection and treatment of asymptomatic infection;

2. Reduce onward transmission to sexual partners;

3. Prevent the consequences of untreated infection;

4. Test at least 25 percent of the sexually active under 25 population annually.

5. Retest after treatment.

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.

In Belgium the prevalence of nosocomial infections is about 6.2%. Annually about 125,500 patients become infected by a nosocomial infection, resulting in almost 3000 deaths. The extra costs for the health insurance are estimated to be approximately €400 million/year.