With 2018 rapidly approaching, we at Outbreak Observatory wanted to take a quick look back at 2017 to highlight some of the most interesting and important outbreaks and potential drivers of infectious disease outbreaks from this year. These examples illustrate the need to stay on the ball when it comes to outbreak prevention, detection, and response.

With the exception of #1 on the list—as the situation in Yemen is far and away the worst health and humanitarian emergency of 2017—these topics are not ranked in any particular order. We made no attempt to quantify or compare the magnitude or impact of these events against one another:

10. Vaccine-Preventable Diseases

A growing trend of vaccine hesitancy in many developed countries has led to increased incidence of many vaccine-preventable diseases. The US has faced a number of significant outbreaks of such diseases in recent years, including measles, mumps, and pertussis in 2017. As of December 16, the CDC reported 122 cases of measles (more than 40% higher than 2016); 5,421 cases of mumps (considerably higher than every year since 2000 except 2006 and 2016); and 15,209 cases of pertussis (commensurate with annual incidence since 2000, but 5-10 times that seen in the 1970s/80s). The UK is facing similar challenges, with low vaccination coverage contributing to a sizeable measles outbreak. As of December 19, Public Health England has reported 99 confirmed cases across 5 areas of England. Despite the recent uptick in cases and outbreaks in the US, the UK, and elsewhere, the WHO announced that global measles mortality in 2016 fell below 100,000 deaths for the first time in recorded history, illustrating the impact of global vaccination efforts.

December 14: https://www.outbreakobservatory.org/outbreakthursday-1/12/14/2017/the-uk-battles-measles-outbreak
December 7: https://www.outbreakobservatory.org/outbreakthursday-1/12/7/2017/the-rise-of-mumps-in-the-united-states
August 24: http://www.baltimoresun.com/news/opinion/oped/bs-ed-op-0825-vaccination-delay-20170824-story.html
May 25: https://www.outbreakobservatory.org/outbreakthursday-1/5/25/2017/measles-on-the-rise-in-the-us

9. Viral Hemorrhagic Fevers

In the wake of the West Africa Ebola epidemic in 2013-16, we saw several reports of Ebola and similar diseases in Africa. Despite their pandemic potential, these outbreaks were met with swift and effective responses by national and international organizations. An Ebola outbreak that began in May 2017 in the Democratic Republic of Congo immediately garnered global attention as discussion began regarding the potential use of investigational vaccines. The outbreak ultimately resulted in 8 cases, including 4 deaths, and 583 identified contacts. The WHO announced the end of the outbreak on July 2, 42 days (corresponding to two 21-day incubation periods) after the last patient tested negative for Ebolavirus infection. While a clinical vaccine trial protocol was developed, the size of the outbreak, the effective response by national and international agencies, and logistical challenges (eg, transporting and storing the vaccine) ultimately resulted in the trial not being conducted. Uganda responded well to a Marburg outbreak that occurred during the Global Health Security Agenda Ministerial Meeting in Kampala. The WHO’s final update on November 15 reported 3 cases, all of whom died. Contract tracing identified 339 total contacts in Uganda and Kenya, all of whom had either completed their 21-day monitoring period or were scheduled to on November 16.

November 2: https://www.outbreakobservatory.org/outbreakthursday-1/11/2/2017/uganda-fights-marburg-outbreak-while-hosting-high-level-ghsa-summit
June 1: https://www.outbreakobservatory.org/outbreakthursday-1/6/1/2017/drc-ebola-outbreak-vaccine-update
May 18: https://www.outbreakobservatory.org/outbreakthursday-1/5/18/2017/drc-ebola-outbreak

8. Vectorborne Diseases

After all the attention on Zika virus in 2016, with the emergence of congenital effects such as microcephaly throughout many other countries in Central and South America—further highlighted by the Olympic Games hosted by Brazil—vectorborne diseases were considerably less of a factor in 2017 than many expected. Despite the lack of attention by the global public, vectorborne diseases remain a widespread and deadly challenge. In addition to the diseases we covered in our posts, ongoing threats include malaria (445,000 deaths and $2.7 billion investment worldwide in 2016), dengue (estimated 390 million infections each year; approximately half of the world’s population at risk), and plague (see #3 Plague in Madagascar below).

September 21: https://www.outbreakobservatory.org/outbreakthursday-1/9/21/2017/roman-holiday-tropical-disease-transmitted-in-italy
August 31: https://www.outbreakobservatory.org/outbreakthursday-1/8/31/2017/forecasting-the-threat-of-infection-after-hurricane-harvey
July 27: https://www.outbreakobservatory.org/outbreakthursday-1/7/27/2017/bridging-the-gaps-in-zika-surveillance
June 29: https://www.outbreakobservatory.org/outbreakthursday-1/6/29/2017/zika-virus-vectors-in-the-united-states
June 8: https://www.outbreakobservatory.org/outbreakthursday-1/6/8/2017/zika-in-india

7. Displaced Populations

The Office of the United Nations High Commissioner for Refugees (UNHCR) reported that the global forced displacement population (eg, due to violence or persecution) totaled 65.6 million people at the end of 2016, and the Internal Displacement Monitoring Centre reports that an average of 25.2 million people are displaced by natural disasters each year. These populations face significant health risks due to crowded living conditions, poor or no access to healthcare, and the absence of health and sanitation infrastructure. Several notable outbreaks among these populations in 2017 include diphtheria in Rohingya refugees in Bangladesh and cholera in Somali refugees in Kenya. The WHO reported in December that diphtheria is “spreading fast” among Rohingya refugees in Cox’s Bazar in Bangladesh. The outbreak saw 2,240 suspected cases and 26 deaths between November 8 and December 25, a number which is expected to increase. The WHO also reported a large cholera outbreak in Kenya that began in early 2017, resulting in 3,967 cases as of November 29. The outbreak has affected both the densely populated capital Nairobi and the Dadaab and Kakuma refugee camps. Dadaab is one of the world’s largest refugee camps, hosting nearly 250,000 refugees and asylum-seekers primarily from Somalia. We also address many of these issues in our coverage of the humanitarian and health crisis in Yemen (#1 below).

6. Hurricanes

The US faced a particularly arduous hurricane season in 2017, taking direct hits from two category 5 storms (Irma and Maria) and one category 4 storm (Harvey). Some reports indicate that Hurricane Harvey—which flooded much of the Houston, Texas metro area—could be the costliest storm in US history, which at $190 billion, would exceed the cost of Hurricane Katrina and Superstorm Sandy combined. In addition to the widespread destruction caused directly by the storms themselves, these types of disasters could pose significant health risks. Many health officials and news outlets voiced concerns about vectorborne diseases, bacterial and fungal contamination, and even biosafety laboratory containment. While the threat from these health risk vary widely, these are certainly issues that health officials need to address proactively with concerted efforts to raise awareness among the public. Additional health concerns may arise as a result of degraded infrastructure systems. Hurricane Maria devastated much of Puerto Rico’s water and electrical systems, and recovery has been a slow process (water; electricity). The inability to access clean water can result in ingestion of dangerous pathogens or chemicals, infection of open wounds, or other health problems. Poor access to reliable electricity can put people at risk for heat- or cold-related risks without heat or air-conditioning; hinder hospital, healthcare facility, or pharmacy operations; or increase health risks to those who require electrically powered home use medical devices (eg, insulin pump, electric wheelchair). Preparedness and education for natural disasters should not be limited to mitigating the immediate effects, and concerted effort is required to prepare for infectious disease-related and longer-term health risks.

October 19: https://www.outbreakobservatory.org/outbreakthursday-1/10/19/2017/the-growing-risk-of-leptospirosis-in-puerto-rico
September 7: https://www.outbreakobservatory.org/outbreakthursday-1/9/7/2017/how-much-should-we-worry-about-mold-after-hurricanes-harvey-and-irma
August 31: https://www.outbreakobservatory.org/outbreakthursday-1/8/31/2017/forecasting-the-threat-of-infection-after-hurricane-harvey

5. Flu Season

While not particularly unique to 2017, flu season is always an important health trend. The Southern Hemisphere flu season was particularly bad, notably in Australia. As experts project that the Northern Hemisphere could expect similar trends for the 2017-18 flu season and reports come in that case counts are rising earlier than usual, it is all that more critical to get vaccinated. While the process of determining the relevant strains in each year’s flu vaccine makes it difficult to match the circulating strains each season, vaccination remains the primary public health tool for mitigating the effects of the annual influenza epidemic. In addition to our weekly Outbreak Thursday posts, Outbreak Observatory also completed our first observation trip to Taiwan to investigate their annual seasonal flu mass vaccination campaign with the goal of identifying important challenges and lessons for other organizations who are interested in implementing similar campaigns for influenza or other vaccine-preventable diseases.

November 9: https://www.outbreakobservatory.org/outbreakthursday-1/11/9/2017/the-2017-18-influenza-season-predicting-the-future-by-looking-to-the-past
October 11-22: https://www.outbreakobservatory.org/taiwan-flu-mass-vaccination

4. Antimicrobial Resistance

The resistance of pathogens to therapeutic microbials has been a growing concern for quite some time. The US identified its first case of pan-resistant bacterial infection (ie, resistant to all available antibiotics), Klebsiella pneumoniae in a woman recently hospitalized overseas. Tuberculosis incidence in the US has been declining steadily since the 1990s; however, imported and travel-acquired cases still pose significant health risks, particularly those that are resistant to frontline antibiotics (ie, multi-drug resistant [MDR] or extensively drug resistant [XDR] tuberculosis). An ongoing MDR TB outbreak in Minnesota is the largest of its kind in the US in recent years. While the number of TB cases, in and of themselves, is not necessarily cause for concern, Minnesota is seeing a sharp increase in the number of drug-resistant cases (from 0-1 in a typical year to 17 since 2016). While antibacterial resistance tends to draw the most attention, bacterial pathogens are far from the only ones affected by emerging resistance. Fungal pathogens, such as Candida auris, are an emerging health threat, with some strains exhibiting resistance to all major classes of antifungal products. The US CDC published its initial clinical alert for C. auris in June 2016, at a time when only a single case had been identified in the US. As of November 30, CDC reported 203 confirmed and suspected cases for 2017 alone.

December 21: https://www.outbreakobservatory.org/outbreakthursday-1/12/21/2017/its-beginning-to-look-like-a-lot-of-tb-resistance
August 3: https://www.outbreakobservatory.org/outbreakthursday-1/8/3/2017/f1pcfsfnioog0bx1ciz13kfchhih7f

3. Plague in Madagascar

Plague (Yersinia pestis) is endemic to Madagascar, with approximately 400 cases each year (about 75% of the global total), but 2017 saw the disease move from remote villages into major cities. Similar to what we saw with Ebola in West Africa, transmission increased significantly once the disease took root in densely populated areas. Interestingly, this outbreak exhibited an unusually high percentage of pneumonic plague cases compared to bubonic plague and occurred. On November 27, the WHO announced that all contacts had completed monitoring and prophylaxis and essentially declared an end to the outbreak. In total, the WHO reported 2,348 cases (confirmed, probable, and suspected) and 202 deaths. Of these cases, 1,791 were pneumonic (>75%). While the outbreak is considered to be over, plague season in Madagascar typically runs through April, so additional endemic cases not directly linked to this outbreak are expected.

October 26: https://www.outbreakobservatory.org/outbreakthursday-1/10/26/2017/plague-in-madagascar-update
October 5: https://www.outbreakobservatory.org/outbreakthursday-1/10/5/2017/rat-race-plague-in-madagascar

2. Hepatitis A

Hepatitis A is often associated with foodborne transmission, as has been seen in high-profile outbreaks in Hawai’i, at Ashton Kutcher’s birthday party, and at a Pennsylvania Chi Chi’s restaurant. Several recent outbreaks in Michigan, California, and Utah are presenting unique challenges for public health and healthcare responders, as the transmission pattern is markedly different from foodborne or point-source outbreaks. These outbreaks are occurring among vulnerable homeless populations and/or drug users, and health officials are having difficulty identifying infected individuals and implementing effective interventions, including vaccination. The latest CDC report shows 674 cases (21 deaths) across multiple California outbreaks, 610 cases (20 deaths) in Michigan, and 102 cases (zero deaths) in Utah. We have also heard from some of our local public health and preparedness colleagues around the country that they expect their cities to face hepatitis A outbreaks in similar populations in the near future, but they are face the challenge of proactively implementing interventions with limited resources in the absence of an actual outbreak. Hepatitis A is not just a domestic issue. Europe has also seen a spike in cases over the past several years, including a non-foodborne outbreak that resulted in more than 2,800 cases across 20 countries between June 2016 and September 2017. Hong Kong identified an increase in non-foodborne hepatitis A cases over the past two years.

July 13: https://www.outbreakobservatory.org/outbreakthursday-1/7/13/2017/hepatitis-a-outbreak-in-michigan
September 14: https://www.outbreakobservatory.org/outbreakthursday-1/9/14/2017/hepatitis-a-causes-public-health-emergency-in-san-diego

1. Yemen

Already facing civil war and famine, Yemen is also currently battling multiple infectious diseases amid the world’s largest humanitarian crisis. The destruction of health and sanitation infrastructure resulting from the ongoing conflict and extreme difficulty in accessing basic health care have created ideal conditions for myriad of infectious disease outbreaks and epidemics to take root and flourish. Last week, the cholera outbreak exceeded 1 million cases since October 2016, and the WHO reported 333 suspect cases of diphtheria since October 2017. Fortunately, what initially appeared to be the early stages of a meningitis outbreak in Yemen was found to be within the expected endemic levels of disease. The UN reported in late November that a recent—and rare—delivery of humanitarian aid included 1.9 million vaccine doses, enough to protect 600,000 children against diphtheria, meningitis, pertussis, pneumonia, and tuberculosis, but many more are needed.

November 30: https://www.outbreakobservatory.org/outbreakthursday-1/11/30/2017/yemen-first-cholera-now-diphtheria
September 28: https://www.outbreakobservatory.org/outbreakthursday-1/9/28/2017/unanswered-questions-from-yemens-cholera-outbreak
August 10: https://www.outbreakobservatory.org/outbreakthursday-1/8/10/2017/meningitis-spreading-in-yemen
July 6: https://www.outbreakobservatory.org/outbreakthursday-1/7/6/2017/cholera-in-yemen-update
June 15: https://www.outbreakobservatory.org/outbreakthursday-1/6/15/2017/cholera-in-yemen


Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly in near-real time to allow others to learn from these experiences in order to improve global outbreak response capabilities.

Photo: Fireworks over Kuwait City, Kuwait; courtesy of Pixabay.