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International Vaccine Access Center Blog

Bill Moss, MD, MPH, is a Professor at the Johns Hopkins Bloomberg School of Public Health and Director of Epidemiology at IVAC. He is a pediatrician and global health expert in childhood infectious diseases and has worked extensively in the areas of measles control and eradication, malaria control, and HIV treatment.


This post originally appeared on The Conversation and is cross-posted here with permission.

By Bill Moss


In the US the risk of getting measles or dying from influenza is greater than the risk of getting Ebola. Jaime R Carrero/Reuters

News that a doctor in New York City tested positive for Ebola sparked mandatory quarantine orders for heath workers returning from West Africa in New York and New Jersey last week. The outbreak has killed nearly 5,000 people in West Africa, but only a handful of cases have been reported in the United States. Still, the virus has sparked widespread fear in the US. Views that Ebola is an exotic disease spreading out of control within Africa, with horrific symptoms, inevitable death, and limited means to prevent transmission are contributing to this fear. However, these fears are fueled by a misunderstanding of risk.

The outbreak is a tragic, public health emergency in urgent need of a massive and coordinated global health response. Fear of contagion is justified in communities where incidence is increasing and where protective measures are limited and health care is stretched beyond capacity.

However, this is not the case in the United States. The perceived risk to Americans is exaggerated. The risk of contracting Ebola in the US or the virus reaching epidemic proportions is very, very low.

The fact is, in the United States the risk of infection with measles virus or death from influenza virus is far greater.

Measles is more infectious than Ebola

Although the outbreak in West Africa is increasing exponentially, Ebola is not as contagious as many other infectious diseases. Transmission requires direct contact with infected body fluids. Measles, influenza and pertussis (whooping cough) on the other hand, are spread by respiratory secretions. They are much more explosive because transmission does not require direct contact with an infected person.

The speed with which an outbreak grows depends on how many additional people are infected by each infectious case and the time interval between infections. To put the current Ebola numbers in context, one person with Ebola will on average infect only 1.5 to 2.2 additional people. The relatively low number of people infected by a single case should make it easier to interrupt transmission. Further facilitating control is the fact that a person with Ebola is most infectious after the onset of signs and symptoms.

By contrast, a person with measles is infectious for several daysbefore they become sick. And a person with measles will on average infect 12 to 18 additional people. This year 594 measles cases have been reported in the United States through September 29th, the most in two decades. These cases represent 18 measles outbreaks in 22 states.

An estimated 122,000 people - mostly children - worldwide died of measles in 2012, about 330 measles deaths every day. In the US the increasing number of measles cases is mostly due to people visiting countries with measles outbreaks and carrying the virus back home and into communities in which large numbers of people are not vaccinated.

Measles is also becoming a public health problem in countries affected by Ebola. Immunization services have ceased in many affected areas as health care workers are redeployed to fight Ebola and the public loses confidence in the health care system. Cases of measles have been reported in Liberia and may spread to neighboring countries and beyond.


Instead of worrying about Ebola, make sure your vaccinations are up to date. Brian Snyder/Reuters

Vaccines and risk perception

As panic over Ebola grows, it’s worth asking why Americans are becoming more complacent to the threat of vaccine-preventable diseases.

Some Americans distrust vaccines and misunderstand the risks and benefits. Most Americans with measles this year were unvaccinated and declined vaccination because of religious, philosophical or personal objections. The largest measles outbreak this year spread within communities in Ohio with low vaccination coverage, with smaller outbreaks in California and New York City.

As with Ebola, early diagnosis, isolation and notification are critical to preventing further spread. Unlike Ebola, we have a highly effective and safe vaccine that can prevent measles. The unvaccinated individuals who developed measles in the United States misjudged the risk to themselves and their communities.

Measles isn’t the only risk. As many as 50,000 people die in the US of influenza virus infection in a single season. Influenza vaccine coverage in the United States during the 2013-2014 season was only 59% among children and 42% among adults, putting those most likely to develop severe disease - young infants and the elderly - at risk.

Again, unvaccinated individuals misjudge the risk and consequences of influenza. The Centers for Disease Control and Prevention tracks deaths due to influenza in children. During the 2012-2013 influenza season, 171 children died of influenza in the United States and 109 children died during 2013-2014 season. Although the influenza season has just started, one child death has already been reported in other words the same number of deaths currently due to Ebola in the United States.

Some may fear of exposing themselves or their children to risk from vaccines, even though these fears have been disproved time and again. They may do so without calculating the real risk of actually contracting the infection that these vaccines prevent. The risk might be masked thanks to herd immunity, but outbreaks of measles and whooping cough show the risk is growing. From January 1 to August 16, 17,325 cases of whooping cough were reported in the United States, a 30% increase over the same period in 2013. In California alone, which is experiencing a particularly large outbreak, 312 people have been hospitalized, most of whom were young infants.

Ebola vaccines are currently in development and testing. Most experts agree an Ebola vaccine would be a welcome tool, even if supplies limit use to health care workers. But this begs another question – how many Americans would be willing to receive an Ebola vaccine?


Bill Moss is Professor, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health; Director of Epidemiology, International Vaccine Access Center at Johns Hopkins University


William Moss receives funding from the National Institutes of Health and the Bill & Melinda Gates Foundation. He is affiliated with the World Health Organization as a member of the Strategic Advisory Group of Experts Working Group on Measles and Rubella.


The Measles Ward at the University Teaching Hospital in Lusaka, Zambia (2003)


Bill Moss, MD, MPH

BillMossDr. Bill Moss is a Professor at the Johns Hopkins Bloomberg School of Public Health and Director of Epidemiology at IVAC. He is a pediatrician and global health expert in childhood infectious diseases and has worked extensively in the areas of measles control and eradication, malaria control, and HIV treatment.

The Measles Ward was empty. The Measles Ward at the University Teaching Hospital in Lusaka, Zambia was always full of children, particularly now at the start of the measles season. But several months after the Government of Zambia conducted their first national mass measles vaccination campaign in 2003, the ward was empty. I was astounded. I took a photograph of the empty ward. It is difficult to see the absence of something, but this was a striking image of the absence of measles – an empty hospital ward – and an image that captured the power of vaccines. A successful mass vaccination campaign can provide sufficient protection to vaccinated children and herd immunity to those few who are not immunized, demonstrating that measles virus transmission can be stopped and a measles ward emptied. Approximately 5% of the hundreds of children admitted to that ward died of measles every year, with more dying who never made it to the hospital, others dying after leaving the hospital, and children weakened by measles. These deaths were stopped. It was invisible, but real.

Measles is a viral infection caused by measles virus and characterized by fever, cough, runny nose, red eyes and a distinctive rash. Well-nourished children with good access to health care rarely die of measles, but about 1 in 1000 can get a severe neurological disease as a result of an immune reaction to measles virus. Undernourished children, however, are at high risk of death from measles. In the most extreme circumstances, such as refugee camps, as many as one quarter of children with measles can die. In the absence of vaccination, almost all children will get measles because of its high contagiousness. Today, it is difficult to imagine that prior to the introduction of measles vaccine fifty years ago, measles killed millions of children each year, with some estimates as high as six to eight million deaths per year due to measles. This is far higher than the number of deaths due to AIDS, tuberculosis, and malaria.

Remarkably, a measles virus strain isolated in the mid-1950s, which formed the basis for most of the commonly used measles vaccines around the world today, continues to provide protection against measles five decades later. We do not need to develop new measles vaccines each year as we do for influenza virus. The vaccine is safe and inexpensive, and two doses are sufficient to provide protection to nearly everyone.

So why does measles still kill tens of thousands of children each year? Why is it still occurring in some of the richest countries of the Americas and Europe? Why, in 2014, do we have more measles cases in the United States during the first quarter of the year than we have had since 1996?

The problem is invisibility, as successful public health programs undermine themselves. The disease goes away, political and public attention are directed elsewhere, rumors and misinformation spread, and risks of the vaccine are perceived to be higher than the risk of disease. Along with the high contagiousness of measles virus, a small drop in the number of vaccinated children can lead to outbreaks.


Photo Credit: Dr. James Chipeta (2010)

Sadly, the empty Measles Ward in Lusaka was full again in 2010, overflowing with children in the hallways, as a result of a large measles outbreak that swept through much of sub-Saharan Africa that year. Routine immunization coverage was not sustained at sufficient levels, vaccination campaigns were postponed, and susceptible people accumulated. Once this tinder was ignited by the introduction of measles virus, a massive epidemic had exploded. In the Americas and Europe, misconceptions about the safety of measles vaccine continues to result in low measles vaccine coverage in some communities, which have led to recent measles outbreaks in California, New York, and Washington state and have put children unable of receiving measles vaccine due to serious medical conditions at high risk.

We have the tools to defeat measles, even the tools to eradicate measles. The global public health community now faces a stark choice: to continue to make progress in measles reduction with the ultimate goal of measles eradication, or have recent successes in measles control lead to a loss in public interest, donor support, and political motivation. This year, World Immunization Week’s challenge to everyone, no matter where you live, is to know which vaccines you need, check that you are up-to-date on your vaccinations, and continue to protect yourself by getting timely vaccinations.. Meeting this challenge will be necessary to ensure that future generations of children do not die of measles and that all measles wards are emptied.

Nov 2014