Open Outbreak

Drug-resistant bacteria and fungi

Also known as: Antimicrobial resistance, AMR, antibiotic resistance, drug-resistant infections, multidrug-resistant organisms

Drug-resistant bacteria and fungi are germs that no longer respond well to medicines that used to kill them or stop their growth. This is usually described as antimicrobial resistance, or AMR. It is not one single disease. It is a problem that can affect many different infections, from urinary tract infections and pneumonia to bloodstream infections and wound infections. Resistant germs can spread between people, in hospitals and care homes, through food and water, and through the environment. Some resistance also spreads when bacteria swap resistance genes. The health impact is large: a major global analysis estimated 1.27 million deaths were attributable to bacterial AMR in 2019, with 4.95 million deaths associated with it. Severity depends on which germ is involved, where the infection is in the body, and whether effective drugs are still available. There is no single vaccine or single cure for AMR. Control depends on infection prevention, careful use of antibiotics and antifungals, testing to find which drugs still work, and development of new treatments.

Key facts

TransmissionVaries by organism. Resistant bacteria and fungi spread through the same routes as the infections they cause: direct contact, droplets for some respiratory infections, contaminated hands and surfaces, food, water, health-care procedures, and environmental exposure. Resistance genes can also spread between bacteria.
Incubationunknown
Case fatalityunknown overall; it varies widely by infection and organism. A 2022 global analysis estimated 1.27 million deaths attributable to bacterial AMR and 4.95 million deaths associated with bacterial AMR in 2019, but not a single overall case-fatality rate.
Reproduction numberunknown
VaccineNo single vaccine prevents AMR as a whole. Some existing vaccines can reduce infections and therefore reduce antimicrobial use, but vaccine availability depends on the specific pathogen.
TreatmentDepends on the organism and which drugs still work on testing. Treatment may require alternative or last-line antimicrobials, plus source control and infection-prevention measures. For some highly resistant infections, options are limited or may not be available in all settings.
ReservoirHumans, animals, food systems, health-care settings, and the environment can all act as reservoirs for resistant organisms and resistance genes.
Endemic regionsWorldwide

Transmission

AMR is not spread in one single way because it is not one single germ. Drug-resistant bacteria and fungi spread through the same routes as ordinary infections: from person to person, on hands and surfaces, through some medical devices and procedures, and in some cases through food, water, or the environment. The resistance part can spread too. Bacteria can pass resistance genes to other bacteria, which helps resistance move between strains and sometimes between species. Health-care settings are a major concern because antibiotic use is high and vulnerable patients are close together. WHO’s 2024 notice on hypervirulent, carbapenem-resistant Klebsiella pneumoniae warned about spread in both hospital and community settings and highlighted the need for standard and contact precautions, isolation, and better lab detection. In plain terms, AMR spreads when infections spread and when resistant strains or genes gain chances to circulate.

Symptoms and severity

There is no fixed symptom list for AMR itself. People become ill from the underlying infection, not from the word “resistance.” Symptoms therefore depend on where the infection is. A resistant urinary infection may cause pain when passing urine and fever. A resistant pneumonia may cause cough, shortness of breath, and low oxygen. A resistant bloodstream infection can cause sepsis, which is a life-threatening body-wide reaction to infection. What resistance changes is the chance that standard treatment will fail or be delayed. That can make illness last longer, increase the need for hospital care, and raise the risk of death. A major global analysis estimated that bacterial AMR was attributable to 1.27 million deaths in 2019 and associated with 4.95 million deaths that year. There is no single overall case-fatality rate because severity varies greatly by organism, drug resistance pattern, and site of infection.

Treatment and vaccines

Treatment depends on finding out which organism is causing the infection and which medicines still work against it. That usually means microbiology testing, sometimes including genetic testing for resistance markers. Doctors may need to use alternative or last-line drugs, and for some infections those options are fewer, more toxic, more expensive, or not available in every country. Good care also includes source control, such as draining an abscess or removing an infected device, and strict infection-prevention measures to stop spread to others. There is no single vaccine against AMR as a whole because AMR covers many different germs. However, vaccines against specific infections can still help by preventing illness and reducing the need for antibiotics. WHO’s 2024 global notice on resistant, hypervirulent Klebsiella pneumoniae said new therapeutic alternatives are needed and stressed stronger laboratory capacity so cases are recognized early and treated appropriately.

Where it occurs

AMR is a worldwide problem. The large global burden studies describe it as affecting all regions, not only one continent or climate zone. Burden and patterns differ from place to place, depending on which organisms are common, how antibiotics are used, laboratory capacity, infection prevention, sanitation, and access to effective treatment. Hospitals and long-term care facilities are important settings because resistant organisms can spread there quickly, but AMR also exists in the community. WHO’s 2024 assessment of hypervirulent, resistant Klebsiella pneumoniae found reports from at least one country in all six WHO regions, while also noting that surveillance is incomplete and true prevalence is probably underestimated. For the public, the key point is that AMR should be thought of as global and local at the same time: it is a worldwide health threat, but the exact resistant germs and risks differ by country, health system, and setting.

Recent history

WHO Disease Outbreak News has not treated AMR as a frequent single-outbreak topic in the same way it covers cholera or Ebola. In this site’s archive for the pathogen key used here, there are 0 archived WHO-style events. The main recent WHO outbreak-style item found in this session is from 2024-07-31, covering a global situation involving hypervirulent Klebsiella pneumoniae with carbapenem resistance. WHO said the strain had been reported in at least one country in all six regions and assessed the global risk as moderate, mainly because surveillance and laboratory detection are still patchy. The broader trend in the literature is that AMR is not a short-lived event but a long-running global problem. The 2024 Lancet analysis extended estimates from 1990 to 2021 and projected forward to 2050, showing that the burden is persistent rather than confined to one outbreak period.

What to watch

The main warning signs are not one case count but changes in pattern. More concerning signals would include resistant strains appearing in new countries or new community settings, not just hospitals; clearer evidence of sustained person-to-person spread; resistance reaching last-line drugs such as carbapenems or antifungals used when other options fail; and reports that hypervirulent strains are also becoming drug resistant. Another warning sign is weak laboratory capacity, because outbreaks can grow unnoticed when testing is limited. WHO’s 2024 notice specifically pointed to the need for better molecular testing, earlier detection, and stronger infection prevention and control. Shortages of effective medicines also matter. If alternative treatments are unavailable, delayed, or unaffordable, the same infection becomes more dangerous. Vaccine supply is also relevant in a broader sense: shortages of vaccines that prevent bacterial infections can increase illness and antibiotic use, which can add further pressure toward resistance.

Related outbreaks

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