HIV develops resistance when it evades the effects of these treatments.

HIV drug resistance reduces the possible HIV medications a person can take due to cross resistance. In cross resistance, an entire medication class is considered ineffective in lowering a patient's HIV viral load because all the drugs in a given HIV class share the same mechanism of action. Therefore, development of resistance to one medication in a class precludes the use of all other medications in the same class. A blood test should be done to determine which drugs may be effective prior to initiation of treatment or during treatment to ensure resistance has not developed.

In 2004, one study estimated the percentage of the American HIV positive population with some form of drug resistance to be 76.3%. Certain intrinsic features of HIV facilitate its widespread resistance, most importantly its extremely high mutation rate.

In their 2017 HIV Drug Resistance Report, the World Health Organization conducted surveys in 14 countries to estimate the prevalence of resistance to HIV medications. One subgroup included only HIV-positive patients who have just initiated antiretroviral therapy in order to assess the prevalence of HIV drug resistance in treatment-naive patients, deemed "pretreatment drug resistance." Resistance to NNRTIs in this patient population ranged from 2.7% (in Myanmar) to 15.9% (in Uganda). Resistance to NRTIs ranged from 0.3% (in Namibia) to 6.8% (in Nicaragua). Resistance to protease inhibitors ranged from 0.3% (in Carmeroon and Myanmar) to 2.6% (in Mexico). Resistance to NNRTI + NRTI combination therapy ranged from 0.2% (in Myanmar) to 4.6% (in Uganda).

Studies have found that men have a higher risk of getting XDR-TB than women. One study showed that the male to female ratio was more than threefold, with statistical relevance (P<0.05) Studies done on the effect of age and XDR-TB have revealed that individuals who are 65 and up are less likely to get XDR-TB. A study in Japan found that XDR-TB patients are more likely to be younger.

Exposure to antiretroviral treatments has led to the evolution of HIV in response to selection pressure that eliminates strains of HIV that do not express resistance mechanisms. Drug resistance occurs in all antiretroviral treatments if patients are non-adherent, meaning that they do not take their medication regimens as prescribed. Lack of adherence may result from unreliable access to the medication, due to prohibitive cost or inadequate supply.

Current medical and scientific opinion is mixed on the most effective treatment methods, but is focused on drug cocktails and the importance of first-line regimens . The World Health Organization advocates a public-health approach to HIV treatment in order to make treatment uniform and available to patients around the world. As of July 2017, the WHO is implementing the Global Action Plan on HIV drug resistance 2017-2021. It is a 5-year initiative intended to help countries around the world manage HIV drug resistance.

Among treatment methods, the World Health Organization acknowledges the importance of successful first-line treatments. First-line treatments are known to affect the virus’ future response to other treatments, making the effectiveness of first-line treatments an issue of vital importance. The most successful treatments are combinations of three drugs used simultaneously, as this greatly reduces the probability of the virus developing resistance.

Carriers who refuse to wear a mask in public have been indefinitely involuntarily committed to regular jails, and cut off from contacting the world. Some have run away from the USA, complaining of abuse.

When HIV-negative children take isoniazid after they have been exposed to tuberculosis, their risk to contract tuberculosis is reduced. A Cochrane review investigated whether giving isoniazid to HIV-positive children can help to prevent this vulnerable group from getting tuberculosis. They included three trials conducted in South Africa and Botswana and found that isoniazid given to all children diagnosed with HIV may reduce the risk of active tuberculosis and death in children who are not on antiretroviral treatment. For children taking antiretroviral medication, no clear benefit was detected.

A study conducted on 452 patients revealed that the genotype responsible for higher IL-10 expression makes HIV infected people more susceptible to tuberculosis infection. Another study on HIV-TB co-infected patients also concluded that higher level of IL-10 and IL-22 makes TB patient more susceptible to Immune reconstitution inflammatory syndrome (IRIS). It is also seen that HIV co-infection with tuberculosis also reduces concentration of immunopathogenic matrix metalloproteinase (MMPs) leading to reduced inflammatory immunopathology.

Blood for blood transfusion is screened for many bloodborne diseases. Additionally, a technique that uses a combination of riboflavin and UV light to inhibit the replication of these pathogens by altering their nucleic acids can be used to treat blood components prior to their transfusion, and can reduce the risk of disease transmission.

A technology using the synthetic psoralen, amotosalen HCl, and UVA light (320–400 nm) has been implemented in European blood centers for the treatment of platelet and plasma components to prevent transmission of bloodborne diseases caused by bacteria, viruses and protozoa.

Blood poses the greatest threat to health in a laboratory or clinical setting due to needlestick injuries ("e.g.", lack of proper needle disposal techniques and/or safety syringes). These risks are greatest among healthcare workers, including: nurses, surgeons, laboratory assistants, doctors, phlebotomists, and laboratory technicians. These roles often require the use of syringes for blood draws or to administer medications.

The Occupational Safety and Health Administration (OSHA) prescribes 5 rules that are required for a healthcare facility to follow in order to reduce the risk of employee exposure to bloodborne pathogens. They are:

- Written exposure control plan

- Engineering controls (Sharps containers, detachable and retractable needles, syringe caps, etc.)

- Safe Work Practices and Safety Devices

- Hepatitis B vaccine available to employees

- Education and post-exposure follow up

These controls, while general, serve to greatly reduce the incidence of bloodborne disease transmission in occupational settings of healthcare workers.

There are 26 different viruses that have been shown to present in healthcare workers as a result of occupational exposure. The most common bloodborne diseases are hepatitis B (HBV), hepatitis C (HCV), and human immunodeficiency virus (HIV). Exposure is possible through blood of an infected patient splashing onto mucous membranes; however, the greatest exposure risk was shown to occur during percutaneous injections performed for vascular access. These include blood draws, as well as catheter placement, as both typically use hollow bore needles. Preventative measures for occupational exposure include standard precautions (hand washing, sharp disposal containers), as well as additional education and preventative measures. Advancements in the design of safety engineered devices have played a significant role in decreasing rates of occupational exposure to bloodborne disease. According to the Massachusetts Sharps Injury Surveillance System, needle devices without safety features accounted for 53% of the 2010 reported sharps injuries. Safer sharps devices now have engineering controls, such as a protective shield over the needle, and sharps containers that have helped to decrease this statistic. These safer alternatives are highly effective in substantially reducing injuries. For instance, almost 83% of injuries from hollow bore needles can be prevented with the use of safer sharps devices.

In couples where the male and female are both HIV positive, conception may occur normally without concern for disease transmission. However, in couples where only one partner is HIV positive, there is risk of transmitting the infection to the uninfected partner. These couples, known as serodiscordant couples, are advised not to engage in unprotected intercourse. Instead, assisted reproductive methods are recommended. In all serodiscordant couples, the infected partner is advised to begin ART so that levels of the infection are undetectable prior to attempting conception.

In couples where the woman is HIV negative and the man is HIV positive, sperm is collected from the male partner using a technique called sperm washing. This process is then followed by intrauterine insemination (IUI) or in vitro fertilization (IVF). Couples may also use donor sperm from a non-infected male if desired.

In couples where the woman is HIV positive and the man is HIV negative, artificial insemination is recommended.

In areas where assisted reproductive techniques such as IUI or IVF are not available, techniques to reduce the transmission of HIV during conception can be attempted to reduce, but not eliminate, the risks. Most importantly, the HPTN 052 trial showed that when HIV infected partners were on ART there was 96% less transmission of HIV and none from partners with undetectable viral loads.

Many serodiscordant couples use pre-exposure prophylaxis (PrEP) to limit transmission of the infection to the uninfected partner. Daily use of PrEP has been shown to decrease transmission of the infection by an average of 63-75%. However, use of PrEP during pregnancy has not yet been studied and its long-term effects are unknown and should not be the only safety feature in the prevention process.

Although assisted reproductive techniques are available for serodiscordant couples, there are still limitations to achieving a successful pregnancy. Women with HIV have been shown to have decreased fertility which can affect available reproductive options. Women with HIV are also more likely to be infected with other sexually transmitted diseases, placing them at higher risk for infertility. Males with HIV appear to have decreased semen volume and sperm motility which decreases their fertility. Antiretroviral drugs may also affect both male and female fertility and some drugs can be toxic to newly developed embryos. Additionally, there have been cases where an HIV-negative partner was infected with the disease despite using processed artificial insemination.

Together, diseases of poverty kill approximately 14 million people annually. Gastroenteritis with its associated diarrhea results in about 1.8 million deaths in children yearly with most of these in the world's poorest nations.

At the global level, the three primary poverty-related diseases (PRDs) are AIDS, malaria, and tuberculosis. Developing countries account for 95% of the global AIDS prevalence and 98% of active tuberculosis infections. Furthermore, 90% of malaria deaths occur in sub-Saharan Africa. Together, these three diseases account for 10% of global mortality.

Treatable childhood diseases are another set which have disproportionately higher rates in poor countries despite the availability of cures for decades. These include measles, pertussis and polio.

Three other diseases, measles, pneumonia, and diarrheal diseases, are also closely associated with poverty, and are often included with AIDS, malaria, and tuberculosis in broader definitions and discussions of diseases of poverty.

In 1994, Stephen Crohn became the first person discovered to be completely resistant to HIV in all tests performed. In early 2000, researchers discovered a small group of sex workers in Nairobi, Kenya who were estimated to have sexual contact with 60 to 70 HIV positive clients a year without signs of infection. Researchers from Public Health Agency of Canada have identified 15 proteins unique to those virus-free sex workers. Later, however some sex workers were discovered to have contracted the virus, leading Oxford University researcher Sarah Rowland-Jones to believe continual exposure is a requirement for maintaining immunity.

More than 300 million people worldwide have asthma. The rate of asthma increases as countries become more urbanized and in many parts of the world those who develop asthma do not have access to medication and medical care. Within the United States, African Americans and Latinos are four times more likely to suffer from severe asthma than whites. The disease is closely tied to poverty and poor living conditions. Asthma is also prevalent in children in low income countries. Homes with roaches and mice, as well as mold and mildew put children at risk for developing asthma as well as exposure to cigarette smoke.

Unlike many other Western countries, the mortality rate for asthma has steadily risen in the United States over the last two decades. Mortality rates for African American children due to asthma are also far higher than that of other racial groups. For African Americans, the rate of visits to the emergency room is 330 percent higher than their white counterparts. The hospitalization rate is 220 percent higher and the death rate is 190 percent higher. Among Hispanics, Puerto Ricans are disporpotionatly affected by asthma with a disease rate that is 113 percent higher than non-Hispanic Whites and 50 percent higher than non-Hispanic Blacks. Studies have shown that asthma morbidity and mortality are concentrated in inner city neighborhoods characterized by poverty and large minority populations and this affects both genders at all ages. Asthma continues to have an adverse effects on the health of the poor and school attendance rates among poor children. 10.5 million days of school are missed each year due to asthma.

HIV infection rates in central Africa are generally moderate to high.

According to current recommendations by the WHO, US CDC and U.S. Department of Health and Human Services (DHHS), all individuals with HIV should begin ART. The recommendation is stronger under the following conditions:

- CD4 count below 350 cells/mm

- High viral load (>100,000 copies/ml)

- Progression of HIV to AIDS

- Development of HIV-related infections and illnesses

- Pregnancy

Women are encouraged to begin treatment as soon as they are diagnosed with HIV. If they are diagnosed prior to pregnancy, they should continue with ART during the pregnancy. If the diagnosis of HIV is made during the pregnancy, ART should be initiated immediately.

Many of these viruses are controlled through laboratory screening tests. These fall into three basic varieties: antibody tests, nucleic acid tests (NAT), and surrogate tests. Antibody tests look for the immune system's response to the infection. Nucleic acid tests look for the genetic material of the virus itself. The third variety are tests that are not specific to the disease but look for other related conditions.

High risk activities for transfusion transmitted infections vary, and the amount of caution used for screening donors varies based on how dangerous the disease is. Most of the viral diseases are spread by either sexual contact or by contact with blood, usually either drug use, accidental needle injuries among health care workers, unsterilized tattoo and body piercing equipment, or through a blood transfusion or transplant. Other vectors exist.

Whether a donor is considered to be at "too high" of a risk for a disease to be allowed to donate is sometimes controversial, especially for sexual contact. High risk sexual activity is defined in many different ways, but usually includes:

- Sex in exchange for money or drugs.

- Men who have sex with men, the most controversial criterion.

- A recent history of sexually transmitted disease.

- Sex with a person who has had a positive test or was at high risk for a disease that can be spread in blood transfusions.

HIV infection rates in eastern Africa are generally moderate to high.

Long-term nonprogressors (LTNPs), sometimes also called "elite controllers", are individuals infected with HIV, who maintain a CD4 count greater than 500 without antiretroviral therapy with a detectable viral load. Many of these patients have been HIV positive for 30 years without progressing to the point of needing to take medication in order not to develop AIDS. They have been the subject of a great deal of research, since an understanding of their ability to control HIV infection may lead to the development of immune therapies or a therapeutic vaccine. The classification "Long-term non-progressor" is not permanent, because some patients in this category have gone on to develop AIDS.

Long-term nonprogressors typically have viral loads under 10,000 copies RNA/ml blood, do not take antiretrovirals, and have CD4+ counts within the normal range. Most people with HIV not on medication have viral loads which are much higher.

It is estimated that around 1 in 300 people with HIV are long-term nonprogressors. Without the symptoms of AIDS, many LTNP patients may not know they are infected.

Genetic traits that confer greater resistance or more robust immune response to HIV are thought to explain why LTNP patients are able to live much longer with HIV than patients who are not LTNP. Some LTNP are infected with a weakened or inactive form of HIV, but it is now known that many LTNP patients carry a fully virulent form of the virus. Genetic traits that may affect progression include:

- Gene mutation. A mutation in the FUT2 gene affects the progression of HIV-1 infection. 20% of Europeans who have that mutation are called "non secretor" because of their absence of a certain type of antigen that also provides strong resistance against norovirus.

- Mitochondrial DNA. Different mitochondrial DNA haplotypes in humans may increase or decrease rates of AIDS progression. Haplotypes associated with more loosely coupled mitochondrial respiration, with reduced ATP and ROS generation, have been associated with faster progression and vice versa.

- Receptor mutations. A low percentage of long-term nonprogressors have been shown to have inherited mutations of the CCR5 receptor of T cell lymphocytes. HIV uses CCR5 to enter these cells. It is believed that the Δ32 (delta 32) variant of CCR5 impairs HIV ability to infect cells and cause disease. An understanding of this mechanism led to the development of a class of HIV medicines, the entry inhibitors. The presence of this mutation, however, is not a unifying theme among LTNPs and is observed in an exceedingly small number of these patients.

- HLA type has also been correlated with long-term non-progressor cohorts. In particular, strong correlations have been found between possessing the class 1 HLA-B*5701, HLA-B*5703, and/or HLA-B*2705 alleles and ability to exert control over HIV.

- Antibody production. All individuals with HIV make antibodies against the virus. In most patients, broadly neutralizing antibodies do not emerge until approximately 2–4 years after the initial infection. At this point, the latent reservoir has already been established and the presence of broadly neutralizing antibodies is not enough to prevent disease progression. In some rare patients, these antibodies emerge earlier and can result in a delayed disease course. These patients, however, are not typically classified as LTNPs, but rather as slow progressors, who will eventually develop AIDS. Induction of broadly neutralizing antibodies in healthy individuals is a potential strategy for a preventive HIV vaccine, as is the elicitation of these antibodies through rationally designed immunogens. Direct production of these antibodies in somatic tissue through plasmid transfection also pose a viable method for making these antibodies available in a large number of humans.

- APOBEC3G protein production. In a small number of people infected with HIV, the virus is naturally suppressed without medical treatment. These people may carry high quantities of a protein called APOBEC3G that disrupts viral replication in cells. APOBEC3G, or "A3" for short, is a protein that sabotages reverse transcription, the process HIV relies on for its replication. This process involves the virus transcribing its singe-stranded RNA genome into double-stranded DNA that is incorporated into the cell's genome. A3 usually stops dormant viruses in the human genome, called endogenous retroviruses, from reawakening and causing infections.

HIV is transmitted by three main routes: sexual contact, significant exposure to infected body fluids or tissues, and from mother to child during pregnancy, delivery, or breastfeeding (known as vertical transmission). There is no risk of acquiring HIV if exposed to feces, nasal secretions, saliva, sputum, sweat, tears, urine, or vomit unless these are contaminated with blood. It is possible to be co-infected by more than one strain of HIV—a condition known as HIV superinfection.

Estimates of the rate of HCV vertical transmission range from 2–8%; a 2014 systematic review and meta-analysis found the risk to be 5.8% in HCV-positive, HIV-negative women. The same study found the risk of vertical transmission to be 10.8% in HCV-positive, HIV-positive women. Other studies have found the risk of vertical transmission to be as high as 44% among HIV-positive women. The risk of vertical transmission is higher when the virus is detectable in the mother's blood.

Evidence does not indicate that mode of delivery (i.e. vaginal vs. cesarean) has an effect on vertical transmission.

For women who are HCV-positive and HIV-negative, breastfeeding is safe; however, CDC guidelines suggest avoiding breastfeeding if a woman's nipples are "cracked or bleeding" to reduce the risk of transmission.

HIV/AIDS has become a chronic rather than an acutely fatal disease in many areas of the world. Prognosis varies between people, and both the CD4 count and viral load are useful for predicted outcomes. Without treatment, average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype. After the diagnosis of AIDS, if treatment is not available, survival ranges between 6 and 19 months. HAART and appropriate prevention of opportunistic infections reduces the death rate by 80%, and raises the life expectancy for a newly diagnosed young adult to 20–50 years. This is between two thirds and nearly that of the general population. If treatment is started late in the infection, prognosis is not as good: for example, if treatment is begun following the diagnosis of AIDS, life expectancy is ~10–40 years. Half of infants born with HIV die before two years of age without treatment.

The primary causes of death from HIV/AIDS are opportunistic infections and cancer, both of which are frequently the result of the progressive failure of the immune system. Risk of cancer appears to increase once the CD4 count is below 500/μL. The rate of clinical disease progression varies widely between individuals and has been shown to be affected by a number of factors such as a person's susceptibility and immune function; their access to health care, the presence of co-infections; and the particular strain (or strains) of the virus involved.

Tuberculosis co-infection is one of the leading causes of sickness and death in those with HIV/AIDS being present in a third of all HIV-infected people and causing 25% of HIV-related deaths. HIV is also one of the most important risk factors for tuberculosis. Hepatitis C is another very common co-infection where each disease increases the progression of the other. The two most common cancers associated with HIV/AIDS are Kaposi's sarcoma and AIDS-related non-Hodgkin's lymphoma. Other cancers that are more frequent include anal cancer, Burkitt's lymphoma, primary central nervous system lymphoma, and cervical cancer.

Even with anti-retroviral treatment, over the long term HIV-infected people may experience neurocognitive disorders, osteoporosis, neuropathy, cancers, nephropathy, and cardiovascular disease. Some conditions like lipodystrophy may be caused both by HIV and its treatment.

The virus that causes AIDS is the best known of the transfusion-transmitted infections because of high-profile cases such as Ryan White, a haemophiliac who was infected through factor VIII, a blood-derived medicine used to treat the disease. Another person who died of medically acquired HIV/AIDS was Damon Courtenay, who died in 1991 due to a bad batch of factor VIII.

The standard test for HIV is an enzyme immunoassay test that reacts with antibodies to the virus. This test has a window period where a person will be infected but not yet have an immune response. Other tests are used to look for donors during this period, specifically the p24 antigen test and nucleic acid testing.

In addition to the general risk criteria for viruses, blood donors are sometimes excluded if they have lived in certain parts of Africa where subtypes of HIV that are not reliably detected on some tests are found, specifically HIV group O. People who have been in prison for extended periods are also excluded for HIV risk.

There are several elements of the Russian prison system that enable the spread of MDR-TB and heighten its severity. Overcrowding in prisons is especially conducive to the spread of tuberculosis; an inmate in a prison hospital has (on average) 3 meters of personal space, and an inmate in a correctional colony has 2 meters. Specialized hospitals and treatment facilities within the prison system, known as TB colonies, are intended to isolate infected prisoners to prevent transmission; however, as Ruddy et al. demonstrate, there are not enough of these colonies to sufficiently protect staff and other inmates. Additionally, many cells lack adequate ventilation, which increases likelihood of transmission. Bobrik et al. have also noted food shortages within prisons, which deprive inmates of the nutrition necessary for healthy functioning.

Comorbidity of HIV within prison populations has also been shown to worsen health outcomes. Nachega & Chaisson articulate that while HIV-infected prisoners are not more susceptible MDR-TB infection, they are more likely to progress to serious clinical illness if infected. According to Stern, HIV infection is 75 times more prevalent in Russian prison populations than in the civilian population. Therefore, prison inmates are both more likely to become infected with MDR-TB initially and to experience severe symptoms because of previous exposure to HIV.

Shin et al. emphasize another factor in MDR-TB prevalence in Russian prisons: alcohol and substance use. Ruddy et al. showed that risk for MDR-TB is three times higher among recreational drug users than non-users. Shin et al.’s study demonstrated that alcohol usage was linked to poorer outcomes in MDR-TB treatment; they also noted that a majority of subjects within their study (many of whom regularly used alcohol) were nevertheless cured by their aggressive treatment regimen.

Non-compliance with treatment plans is often cited as a contributor to MDR-TB transmission and mortality. Indeed, of the 80 newly-released TB-infected inmates in Fry et al.’s study, 73.8% did not report visiting a community dispensary for further treatment. Ruddy et al. cite release from facilities as one of the main causes of interruption in prisoner’s TB treatment, in addition to non-compliance within the prison and upon reintegration into civilian life. Fry et al.’s study also listed side effects of TB treatment medications (especially in HIV positive individuals), financial worries, housing insecurities, family problems, and fear of arrest as factors that prevented some prisoners from properly adhering to TB treatment. They also note that some researchers have argued that the short-term gains TB-positive prisoners receive, such as better food or work exclusion, may dis-incentivize becoming cured. In their World Health Organization article, Gelmanova et al. posit that non-adherence to TB treatment indirectly contributes to bacterial resistance. Although ineffective or inconsistent treatment does not “create” resistant strains, mutations within the high bacterial load in non-adherent prisoners can cause resistance.

Nachega & Chaisson argue that inadequate TB control programs are the strongest driver of MDR-TB incidence. They note that prevalence of MDR-TB is 2.5 times higher in areas of poorly controlled TB. Russian-based therapy (i.e., not DOTS) has been criticized by Kimerling et al. as “inadequate” in properly controlling TB incidence and transmission. Bobrik et al. note that treatment for MDR-TB is equally inconsistent; the second-line drugs used to treat the prisoners lack specific treatment guidelines, infrastructure, training, or follow-up protocols for prisoners reentering civilian life.

Hospitals are primary transmission sites for CRE-based infections. Up to 75% of hospital admissions attributed to CRE were from long-term care facilities or transferred from another hospital. Suboptimal maintenance practices are the largest cause of CRE transmission. This includes the failure to adequately clean and disinfect medication cabinets, other surfaces in patient rooms, and portable medical equipment, such as X-ray and ultrasound machines that are used for both CRE and non-CRE patients.

Thus far, CRE have primarily been nosocomial infectious agents. Almost all CRE infections occur in people receiving significant medical care in hospitals, long-term acute care facilities, or nursing homes. Independent risk factors for CRE infection include use of beta-lactam antibiotics and the use of mechanical ventilation. Patients with diabetes have also been shown to be at an elevated risk for acquiring CRE infections. When compared to other hospitalized patients, those admitted from long-term acute care (LTAC) facilities have significantly higher incidence of colonization and infection rates. Another 2012 multicenter study found that over 30% of patients with recent exposure to LTAC were colonized or infected with CRE. A person susceptible to CRE transmission is more likely to be female, have a greater number of parenteral nutrition-days (meaning days by which the person received nutrition via the bloodstream), and to have had a significant number of days breathing through a ventilator.

Infections with carbapenem-resistant "Klebsiella pneumoniae" were associated with organ/stem cell transplantation, mechanical ventilation, exposure to antimicrobials, and overall longer length of stay in hospitals.

People most likely to acquire carbapenem-resistant bacteria are those already receiving medical attention. In a study carried out at Sheba medical center, there was a trend toward worse Charleson Comorbidity scores in patients who acquired CRKP during ICU stay. Those at highest risk are patients receiving an organ or stem cell implantation, use of mechanical ventilation, or have to have an extended stay in the hospital along with exposure to antimicrobials. In a study performed in Singapore, the acquisition of ertapenem-resistant Enterobacteriaceae to the acquisition of CRE. Exposure to antibiotics, especially fluoroquinolones, and previous hospitalization dramatically increased the risk of acquisition carbapenem-resistant bacteria. This study found that carbapenem-resistant acquisition has a significantly higher mortality rate and poorer clinical response compared to that of the ertapenem-resistance acquisition.

Bacteruria (also known as urinary tract infection) caused by CRKp and CSKp have similar risk factors. These include prior antibiotic use, admittance to an ICU, use of a permanent urinary catheter, and previous invasive procedures or operations. A retrospective study of patients with CRKp and CSKp infection asserted that the use of cephalosporins (a class of β-lactam antibiotics) used before invasive procedures was higher in patients with CRKp infection, suggesting that it is a risk factor.

In a three-year study, the prevalence of CRE was shown to be proportional to the lengths of stays of the patients in those hospitals. Policies regarding contact precaution for patients infected or colonized by Gram-negative pathogens were also observed in hospitals reporting decreases in CRE prevalence.

One case study showed that patients with a compromised immune response are especially susceptible to both CRE exposure and infection. In one study, an elderly patient with acute lymphoblastic leukemia being treated in a long-term care facility contracted a CRE infection. Her age and condition, combined with her environment and regulation by a catheter and mechanical ventilation, all contributed to a higher susceptibility. This highlights the importance of finding the source of the bacteria, as members of this class of patients are at continued risk for infection. Infection control and prevention of CRE should be the main focus in managing patients at high risk.

Another major risk factor is being in a country with unregulated antibiotic distribution. In countries where antibiotics are over-the counter and obtainable without a prescription, the incidence and prevalence of CRE infections were higher. One study from Japan found that 6.4% of healthy adults carried ESBL (mostly cefotaximase)-producing strains compared to 58.4% in Thailand, where antibiotics are available over the counter and without prescription. An Egyptian research group found that 63.3% of healthy adults were colonized.

In February 2015, the FDA reported about a transmission risk when people undergo a gastroenterology procedure called endoscopic retrograde cholangiopancreatography, where an endoscope enters the mouth, passes the stomach, and ends in the duodenum; if incompletely disinfected, the device can transmit CRE from one patient to another. The FDA's safety communication came a day after the UCLA Health System, Los Angeles, notified more than 100 patients that they may have been infected with CRE during endoscopies between October 2014 and January 2015. The FDA had issued its first notice about the devices in 2009.

The U.S. Centers for Disease Control and Prevention (CDC) publishes a journal "Emerging Infectious Diseases" that identifies the following factors contributing to disease emergence:

- Microbial adaption; e.g. genetic drift and genetic shift in Influenza A

- Changing human susceptibility; e.g. mass immunocompromisation with HIV/AIDS

- Climate and weather; e.g. diseases with zoonotic vectors such as West Nile Disease (transmitted by mosquitoes) are moving further from the tropics as the climate warms

- Change in human demographics and trade; e.g. rapid travel enabled SARS to rapidly propagate around the globe

- Economic development; e.g. use of antibiotics to increase meat yield of farmed cows leads to antibiotic resistance

- Breakdown of public health; e.g. the current situation in Zimbabwe

- Poverty and social inequality; e.g. tuberculosis is primarily a problem in low-income areas

- War and famine

- Bioterrorism; e.g. 2001 Anthrax attacks

- Dam and irrigation system construction; e.g. malaria and other mosquito borne diseases

Pregnant women who contract HEV are at significant risk of developing fulminant hepatitis with maternal mortality rates as high as 20–30%, most commonly in the third trimester . A 2016 systematic review and meta-analysis of 47 studies that included 3968 people found maternal case-fatality rates (CFR) of 20.8% and fetal CFR of 34.2%; among women who developed fulminant hepatic failure, CFR was 61.2%.