Experts warn that a global health crisis is on the horizon as drugs available for once treatable diseases are losing their edge. The bacteria, viruses and parasites behind diseases such as tuberculosis, malaria and gonorrhea are fighting back by developing resistance to our arsenal of pharmaceuticals.
With the World Health Organization saying that we could be heading to a "post-antibiotic age," what infections are becoming a concern?
Report by Meera Senthilingam Courtesy of Sage Ross, Wikimedia Commons
Malaria (insert: Plasmodium falciparum)
Malaria was a target for global eradication in 1955 using the once potent drug chloroquine as the weapon of choice to kill the plasmodium parasites behind the disease. However, resistance to the drug developed and spread rapidly across the world rendering the drug, and hope of eradication, useless by the 1970s.
A new wave of excitement came soon after with the arrival of artemisinin, which is today prescribed as a combination therapy to avoid the development of resistance. Despite this strategy, resistance has been reported in Cambodia and could once again spread globally. Globalization and increasing travel to remote locations means the 200 million cases of malaria estimated to occur each year are not just a concern for developing countries.
Courtesy TANG CHHIN SOTHY/AFP/GettyImages and CDC
HIV (insert: Human immunodeficiency virus)
The arrival of antiretroviral therapy changed the face of the HIV epidemic globally from a chronic, debilitating and inevitably fatal infection to one that can be managed to live a long and healthier life.
But the virus reproduces rapidly, meaning resistant forms could easily form and multiply. Up to 14% resistance was found in high-income countries soon after antiretrovirals were introduced in the 1990s and increased use of treatment in developing countries has seen resistance emerge more globally. In 2012, 35 million people were estimated to be living with HIV, based on World Health Organization reports, and with over 2 million people newly infected in 2012, HIV could one day return to pandemic levels if resistance continues to spread. CHRISTOPHE ARCHAMBAULT/AFP/Getty Images and NIAID
Tuberculosis (insert: mycobacterium tuberculosis)
Tuberculosis almost disappeared in the majority of the Western world as countries developed. But the disease persists globally, with an estimated 8.6 million people developing TB in 2012 and 1.3 million dying from it.
The bacterium behind the disease, Mycobacterium tuberculosis, has developed not only multidrug resistant but also extensively drug resistant forms of the disease, which require an additional pool of more toxic drugs. In 2012, there were 450,000 cases of MDR-TB worldwide and XDR-TB was reported in 92 countries. Countries such as India have reported patients with total resistance to all drugs. With few new drugs in the pipeline to control the bacteria, total resistance could spread. ALEXANDER JOE/AFP/Getty Images and CDC
Typhoid Fever (insert: Salmonella typhi)
Immunization remains the weapon of choice in controlling typhoid fever. The disease still affects 21.5 million people in developing nations, and increased global travel means the disease is not limited to those countries. The United States sees over 5,000 people infected each year after consuming contaminated food and drink abroad.
The bacterium behind the disease, Salmonella typhi, can be killed with various antibiotics, but resistance is now arising to multiple antibiotics and complicating treatment, especially in South Asia, a popular holiday destination. AHMAD AL-RUBAYE/AFP/Getty Images and CDC
Hospital acquired Infections (insert: Klebsiella)
Multidrug-resistant Staphylococcus aureus, which causes a range of symptoms from boils and abscesses to blood poisoning and arthritis, has been a concern for years in hospitals and whilst public health teams have been tackling it, a group of bugs known as the ESKAPE pathogens is taking the lead.
Standing for Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter, the ESKAPE pathogens cause a range of symptoms including pneumonia, urinary-tract infections, septicemia, meningitis and diarrhea. If resistance continues to rise, WHO reports highlight that a routine hospital visit could result in a more serious condition. Joe Raedle/Getty Images and NIAID
Gonorrhea (insert: Neisseria Gonorrhoea)
Globally, there are an estimated 88 million cases of this sexually transmitted infection, caused by the bacterium Neisseria gonorrhoeae, each year. Resistance to antibiotics began to occur soon after their introduction in the 1930s and has continued to rise with resistance now seen against five of the drugs once used to treat it -- which include the commonly used antibiotics penicillin and tetracycline.
Only one class of drug, cephalosporins, remains with the ability to fight the bacteria, but resistance to this last resort has now occurred in 10 countries. If this spreads globally, gonorrhea could become untreatable and spread rapidly throughout a promiscuous population. LEO RAMIREZ/AFP/Getty Images and CDC
Influenza (insert: influenza virus)
Influenza virus types A and B sweep through countries annually in the winter months; they cause fever, headaches and muscular pain in most cases, but also cause 3 million to 5 million cases of severe illness and 250,000 to 500,000 deaths each year, according to the WHO The antiviral drugs oseltamivir and zanamivir are the main means of fighting infection. Preventative antivirals amantadine and rimantadine were once used to control seasonal spread, but high levels of resistance means their use is no longer recommended.
The constantly evolving biology of the influenza virus means that resistance can easily form. Amantadine-resistant viruses began emerging in 2003 and oseltamivir-resistant viruses since 2007. Resistance to zanamivir has also been reported. While the majority of viruses found globally are still sensitive to the key drugs, the resistant forms could easily spread as no other drug options remain available. Tom Grill/Getty Images and CDC