From rashes to puffy cheeks and persistent coughs, infectious diseases are a complex, everyday threat to human health. The introduction of vaccines was a revolutionary step in combating epidemic viruses and bacteria. However, during an age in which herd immunity is slipping and multidrug-resistant pathogens are on the rise, spotting infectious diseases can feel similar to detective work for many primary care physicians.
The World Health Organization (WHO) currently list 26 infectious global diseases as vaccine-preventable or potentially preventable. Many of the diseases listed are seldom, if ever, encountered by physicians in high-income countries.
Some of the most common and serious ones have, however, recently made a comeback. What is worse is that these were once considered eliminated or near elimination in these regions.
In the United States and Europe, resurgences have been recorded for three diseases for which vaccines are universally recommended in childhood: measles, mumps, and pertussis (or whooping cough). Other diseases such as tuberculosis (TB) are reappearing as multidrug-resistant (MDR) forms.
In the U.S. and many other countries, measles, mumps, pertussis, and TB are classed as notifiable conditions that must be reported to local and national public health authorities. This must be done as soon as they have been diagnosed, so that immediate action can be taken to curtail the spread of the virus or bacterium.
However, each disease presents specific challenges that may result in delayed diagnosis and allow further spread of the infection. An article published in Academic Pediatrics reports that the median public health cost of each recent measles outbreak in the U.S. is between $71,000 and $179,000. In 2011, the U.S. experienced 16 measles outbreaks, the associated cost of which a paper in Vaccine estimated to be in the region of $2.7 million to $5.3 million.
Spotting these diseases can, in some cases, be quite a challenge for family practitioners and other primary care physicians (PCPs). Medical News Today spoke to William Schaffner, M.D., professor of preventative medicine and infectious diseases specialist at Vanderbilt University School of Medicine in Nashville, TN, about measles, mumps, pertussis, and TB, as well as tips for spotting them.
Unvaccinated people are most vulnerable to measles
Measles was declared as eliminated in the U.S. in 2000.
However, outbreaks of between 50 and 100 cases continue to occur each year and recently reached a peak of 667 cases reported nationwide in 2014.
The majority of measles outbreaks nowadays occur in unvaccinated individuals after coming into contact with infected individuals traveling from countries where measles is still endemic.
"Measles is the probably most highly transmissible infection that we know [of]," Dr. Schaffner told MNT.
Virus transmission that traced back to outbreaks in the Philippines and France led to the outbreaks recorded in 2014 to 2015 and 2011, respectively, in the U.S.
"With the prompt public health response, outbreaks are rapidly curtailed, but they are very vexing," Dr. Schaffner commented.
"Because some parents are withholding their children from vaccination, there is the opportunity for reintroduction and the re-establishment of measles in the U.S.," he stressed.
Outside the U.S., measles remains endemic in 14 European countries, including France, Germany, Italy, and Switzerland.
Large measles outbreaks are ongoing in Romania and Italy.
As a result, the number of measles cases reported annually is rising in Europe, despite measles having been declared eliminated in 24 European countries.
Mumps cases increasing despite vaccination
Cases of mumps in the U.S. have dropped by 99 percent since a vaccine was introduced in 1967. Outbreaks still occur, however - especially among close-contact communities such as college campuses.
Mumps infections often originate in Europe and can become established in these communities before leaking out into the wider population.
Mumps is endemic worldwide, despite its vaccine being routinely used in 61 percent of countries.
In the U.S., 5,748 mumps cases were reported in 2016, the highest level for 10 years.
Yet each outbreak usually affects only a few hundred people, typically adolescents or young adults. Importantly, most cases occur in individuals who have received a mumps-containing vaccine.
"Unlike measles and rubella, which offer lifetime protection, we have come to learn that after about 15 years, protection with [a] mumps vaccine wanes. If an individual whose protection has waned is exposed intensely, such as through prolonged face-to-face contact, they can acquire mumps, although almost always in a much milder form."
William Schaffner, M.D.
The currently available mumps vaccine is rated as 78 percent effective after one dose, and 88 percent after the second dose. The Centers for Disease Control and Prevention (CDC) have issued guidance for use of a third dose in specific target populations, and its Advisory Committee on Immunization Practices are currently evaluating the potential benefits and harms of adding a third dose for routine use.
Many physicians in high-income countries may never have seen a case of measles or mumps. The classic triad of cough, conjunctivitis, and coryza, along with a rash, is the key, but it can easily be overlooked when a child presents with measles. "Often it will be an older physician or nurse who recognizes it," Dr. Schaffner said.
In cases of mumps, the typical swelling in the cheeks is usually so prominent that it tends to get diagnosed more promptly, but "physicians practicing in areas with colleges and travelers from abroad should have a higher index of suspicion," Dr. Schaffner advised.
Pertussis still endemic in the U.S.
Pertussis was one of the most common childhood diseases in the U.S. before a vaccine became available.
After widespread vaccination began in the 1940s, the incidence of pertussis decreased by more than 75 percent, but from the 1980s onward, the number of cases started to rise again.
In 2012, the last peak year, 48,277 cases of pertussis were reported, the highest number since 1955. Currently, pertussis is considered the most common vaccine-preventable disease in the U.S.
The CDC believe that many more cases may go unrecognized, since clinical presentation of the disease in adolescents and adults can be much milder than in children.
Pertussis incidence rates in other high-income countries have also risen, notably in Europe and particularly in the United Kingdom and the Netherlands, as well as in Australia. "Once again, this is an illness we had hoped to eliminate completely but have not yet been successful at doing so," Dr. Schaffner commented.
A number of reasons have been proposed for the increases in reported cases, including vaccine refusal, increased surveillance, and reporting of pertussis to public health departments. The switch in high-income countries from whole-cell to acellular pertussis vaccines has also been implicated. Dr. Schaffner identifies two main factors in the U.S. - the first is waning immunity from vaccination, and the second is genetic mutation of the bacterium Bordetella pertussis.
"The vaccine we use is very effective in the short-term, but after only about 5 years its protection wanes partially, so we have had continuing transmission of pertussis in many parts of the country," he told MNT. Whether the bacterium has mutated such that its characteristics now enable it to evade the vaccine continues to be an issue of ongoing scientific debate and research, he noted.
In cases of pertussis in children, the cough is extremely predominant and very recognizable, whereas in adults, the cough is usually milder but extremely persistent. However, in its early stages, it may resemble the common cold and may not be suspected or diagnosed until the more severe symptoms appear.
Emergence of MDR-TB
TB has re-emerged globally due to the evolution of MDR strains of the causative bacterium, Mycobacterium tuberculosis, which, through mutation or genetic exchange, have acquired resistance to the antibiotics used to treat the disease.
In the U.S., the incidence of TB was declining until the year 2013. This followed the public health response to an epidemic of an MDR strain in the 1990s, which led to a decrease in incidence of 67 percent within 5 years.
Since 2013, however, the incidence has leveled out at around 3 cases per 100,000 people. Two thirds of cases of active TB in the U.S. occur among foreign-born residents, often years after their arrival in the country. The U.S. is not the only high-income country to see a stall in TB decline; in Europe, there were 70,000 reported cases of MDR-TB in 2016.
A recent article in The Lancet warned that "every year, strains of drug-resistant tuberculosis will emerge that are more transmissible, more difficult to treat, and more widespread in the community," and that an MDR-TB epidemic "of unprecedented global scale" is possible within the next decade.
Family practitioners "need to be aware that a puzzling lung disease which seems not to be responding to conventional antibiotics might be TB," cautioned Dr. Schaffner. A key question to ask every patient who presents with a respiratory infection is whether they have been traveling, and if so, which countries they have been to. Practitioners should be on the alert for individuals who come in with latent TB infection who do not appear ill, he stressed.
Avoid overprescribing antibiotics
Another challenge is to avoid overprescribing antibiotics at the first hint of infection, Dr. Schaffner said. "Physicians must be extremely attentive to the results from the microbiology laboratory to ensure that that they have chosen the appropriate antibiotic. PCPs have to avoid prescribing to patients expecting an antibiotic and instead provide knowledge and education."
"Doctors will tell you that by the end of the day they are more likely to write the prescription than, for the umpteenth time, go through a mini-lecture and tell patients they don't need an antibiotic, because it is always a bit contentious, because the patient has an expectation and is in a sense disappointed."
William Schaffner, M.D.
Progressive resistance of bacteria to antibiotics is a major concern throughout the whole world, and a current priority for the WHO, Dr. Schaffner stressed. "It is very important for physicians to be knowledgeable about what the antibiotic resistance circumstances in their communities [are]," he said. "It is a lot for a PCP to keep up with, but it is a consequence of our smaller world."
Whether it is a viral or a bacterial culprit, large-scale vaccination programs are the best defense against many infectious diseases. Spotting the early signs of these can be challenging, but remaining on the lookout for symptoms of measles, mumps, pertussis, and TB is key to protecting patients and communities from epidemics.