Mumps: How It Spreads, Outbreaks, MMR Vaccine, and More

History

Mumps virus discovery

The earliest reference to mumps is from the 5th century BC when Hippocrates, the Father of Medicine, described the symptoms in his first book on epidemics [6]. However, the cause of the disease remained unknown till 1908, when Granata first suggested that a virus was responsible. 

In 1935, Claud Johnson and Ernest Goodpasture finally proved that a virus causes the disease. They injected monkeys with an unknown virus found in the saliva of people with early symptoms of mumps. When the monkeys began to develop symptoms of the disease, they confirmed that a virus caused mumps [2]. 

Mumps vaccine discovery

While mumps affected many children, deaths and severe complications were rare. So, unlike influenza, smallpox, and polio, there was no strong public demand for a vaccine. However, mumps infections significantly reduced productivity and workforce effectiveness. During wartime, particularly World War I and World War II, the military struggled with having too many of its soldiers fighting the mumps virus. This was one of the reasons why there was continued interest in finding a vaccine for mumps [7, 17].

But, it was only in 1945 that Karl Habel of the U.S. Public Health Service first cultured the mumps virus from embryonated eggs of hens. The following year, Habel developed the first experimental mumps vaccine with a weakened virus and tested its effectiveness on 2,825 West Indian sugarcane plantation workers in Florida. At the time, crowded living quarters made mumps infections spread faster, taking them away from work until recovery. Although some vaccinated workers did catch the disease, symptoms were mild. Overall, the vaccine was deemed effective [7, 17]. 

In 1956, the former Soviet Union was the first to develop a live mumps vaccine [7]. However, the quest for an effective vaccine continued in the United States. A breakthrough occurred in 1963. A six-year-old girl named Jeryl Lyn began to experience a sore throat and swollen glands. Her father, Maurice Hilleman, happened to be the head of Virus and Cell Biology at Merck, an upcoming pharmaceutical company at the time. Hilleman used his daughter’s saliva swab to isolate the mumps virus and develop an attenuated mumps vaccine that he named Mumpsvax. In 1967, the US FDA authorized and licensed Mumpsvax for general use [7, 17].  

The MMR vaccine (Measles-Mumps-Rubella)

In 1971, Merck released the MMR, a combined vaccine against measles, mumps, and rubella. [2,7]. In the same year, the Advisory Committee on Immunization Practices (ACIP), a committee within the US Centers for Disease Control and Prevention (CDC), recommended a single dose of the MMR vaccine for general use. In 1989, the committee suggested that all children be given two shots of the vaccine for better effectiveness [7,17].

The MMRV vaccine (Measles-Mumps-Rubella-Varicella)

In 2005, Merck added the varicella vaccine to the MMR. It became known as the measles, mumps, rubella, and varicella (MMRV) vaccine [2]. By 2015, over 60% of member states of the World Health Organization (WHO) recommended at least one dose of the mumps-containing vaccine [7].

Epidemiology

Mumps occurs worldwide through all seasons [2]. In temperate regions, cases peak during winter and spring. Children and young adults are the most affected. Boys are more likely to develop complications than girls [1]. Other high-risk groups include college and university students, healthcare workers, military personnel, and international travelers [7].

During the pre-vaccination era, the disease was commonly known as a childhood illness, as most people were infected as children [8]. During this period, 40 to 726 cases per 100,000 population were reported annually. Outbreaks mainly occurred in crowded places, such as schools, military barracks, prisons, etc. [9]. 

Notable Outbreaks

• During World War I, mumps was one of the leading causes of morbidity among the US military forces stationed in France. There were over 50 hospitalizations for every 1,000 cases each year.
• Mumps was also one of the leading causes of morbidity among soldiers during the American civil war and World War II [7] 
• In 1968, around 152,000 mumps cases were reported in the US, and it became a nationally notifiable disease in the country [2].

Since the mump vaccine was introduced, the world has witnessed a gradual drop in cases. By 2001, mumps was on the verge of becoming a rare disease, with a 99.9% decrease in cases compared to the pre-vaccination period. But, within a few years, outbreaks began to re-appear in certain parts of the world [6]. They include Belarus, Canada, Israel, Moldova, the Netherlands, the UK, the US, etc. [10].

• In 2005, around 56,000 cases were reported in the UK. College and university students were the most affected. Many affected were unvaccinated and, at the time of infection, over the age limit eligible to receive the vaccines.
• In 2006, over 5,800 cases were reported across the US, particularly in Iowa. The demographics of the affected population were similar to that of the UK. It was college and university students between 18 and 24 years old. Unlike the UK, most people who were infected in the US have been vaccinated [1]
• In the same year, the Czech Republic, a country in Central Europe, reported around 5,998 cases. However, no deaths were reported, and nearly 21% of patients were hospitalized [11]. Despite its massive vaccination efforts, Israel reported over 5,000 cases between 2009 and 2010, raising questions regarding the effectiveness of its vaccination policies [12]
• Around 4,061 cases were reported in Belgium between 2012 and 2013 [13]. An outbreak immediately followed this in Poland, where 2,431 cases were reported [14]. Like Israel, many cases reported in Belgium and Poland were vaccinated with at least one dose of the mumps-containing vaccine [13,14]
• In the US, over 1,000 mumps cases have been reported annually since 2014. Between 2016 and 2017, around 150 outbreaks occurred in the country, with over 9,000 cases reported from 37 states. In 2019, mumps raised concerns as almost all states reported cases [2].

How is it spread?

Mumps is contagious and spreads from person to person in the following ways:

• Airborne respiratory droplets from when an infected person coughs, sneezes, or talks
• Sharing bottles, cups, glasses, or spoons contaminated with the saliva of an infected person
• Involving in activities that require close contact with the infected person, such as sports, dancing, or kissing [3]

Biology of the disease

The mumps virus has a single-stranded RNA genome. Once the mumps virus enters the respiratory tract, it replicates in the nasopharynx – the upper part of the throat behind the nose, and the regional lymph nodes. As the virus spreads and the viral load in the blood increases, it spreads to the meninges, salivary glands, pancreas, testes, and ovaries, causing inflammation [2]. The virus is self-limiting in most instances, which means people can usually recover on their own without treatment.

Symptoms

Symptoms of mumps are usually mild, and most people recover fully within two weeks. Many people can be asymptomatic and may not even know they are infected. But, for some people, severe complications can occur, especially in adults [4,15]. 

It takes 2 – 4 weeks for symptoms to appear after exposure to the virus [4]. 

Early symptoms of mumps are: 

• Headache
• Muscle pain
• Low-grade fever
• Fatigue
• Loss of appetite.

Symptoms that appear after the first few days include inflammation of the salivary glands on either side of the face. This condition is referred to as parotitis. During this phase, patients have:

• Puffy cheeks
• Tender and swollen jaws [4,15]. 

Some of the complications can include the following:

• Inflammation of the testicles (occurs in 20% of young men who develop mumps) [4]
• Deafness
• Inflammation of the ovaries
• Inflammation of the breast tissue
• Inflammation in the pancreas
• Inflammation of the brain and spinal cord – encephalitis [16].

Diagnosis

A person with inflammation in the parotid gland can be suspected to be infected with the mumps virus. In such cases, laboratory testing can be done to confirm the presence of the virus. RT-PCR and viral culture are the commonly used diagnostic methods to detect the presence of mumps virus in buccal, oral, or urine samples. But, a negative test result cannot be considered 100% accurate, especially in people exhibiting clinical signs and symptoms [2]. 

Suppose the virus cannot be detected either through RT-PCR or viral culture. In that case, a serological confirmation can be made based on measuring the level of virus-specific IgM antibodies through direct or indirect ELISA [1]. 

Treatment

Currently, there is no medical treatment for mumps. Patients are given supportive care to address the symptoms. They include:

• Medications (ibuprofen or cold packs) to relieve pain as a result of inflammation of the salivary glands located on either side of the face.
• Treatment to relieve headaches patients may develop due to meningitis [1,8].

Doctors may advise an anti-inflammatory diet that avoids fatty foods, acidic food like tomatoes or lemons, spicy food, and raw vegetables until recovery.

Prevention

The mumps vaccine greatly lowers the risk of getting infected with mumps. National immunization programs around the world reduced the global incidence of mumps. A single shot is almost 80% effective in protecting against the disease [1]. Although breakthrough infections are possible, the MMR and MMRV reduce the severity of symptoms among those infected. 

The MMR and MMRV vaccines both contain the live (but weakened) mumps virus: 

• MMR vaccine: Administered to children 12 months of age or older. Two doses of the vaccine are recommended with a gap of at least four weeks or a month in between. The first dose is administered between 12 and 15 months of age. The second dose is administered between four and six years of age. Unvaccinated adults should receive at least one dose of the MMR vaccine. 
• MMRV vaccine: Administered to children between 1 and 12 years of age. It cannot be given to those over 13 years. The first dose should be administered before the child turns four years. The second dose can be administered within three months after the first dose [2]. 

The GIDEON Difference

GIDEON is one of the most well-known and comprehensive global databases for infectious diseases. Data is refreshed daily, and the GIDEON API allows medical professionals and researchers access to a continuous stream of data. Whether your research involves quantifying data, learning about specific microbes, or testing out differential diagnosis tools – GIDEON has you covered with a program that has met standards for accessibility excellence.

ALREADY A SUBSCRIBER?

Learn more about mumps on the GIDEON platform.