Canada is seeing a resurgence of measles, with cases in the first quarter of 2024 already far surpassing the total for all of 2023. There were 12 cases last year, and more than three times that number so far in 2024, with 38 reported as of March 19.
As an immunologist with a focus on host-microbe interactions and antiviral immunity, I have been following recent measles outbreaks.
Symptoms and complications
Measles (also known as rubeola) is a serious but vaccine-preventable disease caused by an RNA virus of the family Paramyxoviridae.
Measles usually begins with fever, runny nose, conjunctivitis (red watery eyes), sore throat and coughing. These can be initially mistaken for common cold or flu.
However, these non-specific signs and symptoms are typically followed by clinical manifestations that are characteristic of measles. These include Koplik spots (tiny white specks with bluish-white centres in the inner lining of the cheeks), and subsequently a measles rash appearing on the face before spreading downward to other areas of the body.
In most cases, measles resolves on its own. However, severe complications may arise, especially in immunocompromised individuals. Complications can include pneumonia, encephalitis (brain inflammation and swelling), blindness, deafness and permanent neurological consequences. When measles occurs during pregnancy, it can result in miscarriage, premature labour, stillbirth, birth defects or even fetal death. The most severe cases of measles can be fatal.
Also of note, infection with the measles virus can weaken the immune system for months or years, increasing the risk of infections with a wide range of microbes. While measles-associated immunosuppression has been documented for decades, we are only beginning to decipher its underlying mechanisms. For example, a phenomenon called “immune amnesia” is thought to contribute, at least partially, to unrelated infections in the aftermath of measles.
What is immune amnesia?
The naturally occurring (wild-type) strains of measles virus can target, infect and kill memory B and T lymphocytes, which are instrumental to antimicrobial defence. This is because one of the three measles virus receptors, called CD150, happens to be abundantly present on the surface of these lymphocytes.
Long-lived memory cells, which accumulate as a result of immunizations and infections over time, remain in a poised state to mount rapid and rigorous recall responses when we re-encounter microbes. B cells orchestrate the production of antibodies that neutralize extracellular microbes, and T cells work to destroy infected cells. Therefore, when people lose their precious memory cells to measles, the immune system is set back to a default mode, as if it has never seen any microbes or vaccines in the past.
To add insult to injury, measles virus may also eliminate “memory-like” innate T cells, which also express CD150, thus removing yet another potent weapon from our antimicrobial arsenal. Therefore, collectively, the ability of measles virus to find and kill memory and memory-like lymphocytes can lead to adaptive and innate immune amnesia, rendering a measles patient or survivor prone to many opportunistic infections.
How does measles spread and how contagious is it?
Measles virus spreads easily through airborne droplets released by infected people when they breathe, talk, laugh, cough or sneeze. In addition, measles virus infectious particles can remain active in the air and on contaminated surfaces for up to two hours.
Measles vaccines are safe, affordable and extremely effective. According to the World Health Organization (WHO), measles claimed 2.6 million lives each year before 1963 when a measles vaccine became available. Since then, widespread immunization programs have saved millions of lives, including an estimated 56 million just between 2000 and 2021.
Measles vaccines contain a live measles virus strain that has been attenuated so that it does not inflict harm; yet, it is sufficient to generate protective immune responses.
The measles-mumps-rubella (MMR) vaccine or the measles-mumps-rubella-varicella (MMRV) vaccine is routinely administered to children in two doses, with a first dose being given after the first birthday, typically between 12-15 months of age, followed by a booster dose recommended after 18 months of age and before attending school. This should afford lifelong protection against measles in most people.
According to the United States Centers for Disease Control and Prevention (CDC), one and two doses of the MMR vaccine are 93 per cent and 97 per cent effective in preventing measles, respectively.
Teens and adults should also remain up to date with regard to measles immunization since measles can affect anyone. There are blood tests that can be ordered by health-care providers to determine immunity to measles.
The MMR vaccine can be given at any time during one’s lifespan, but the MMRV vaccine is authorized in Canada only between one and 13 years of age.
Measles outbreaks occur soon after herd immunity is compromised. Herd immunity is achieved when an adequately large proportion of a population becomes immune to a specific pathogen through prior infections or vaccination. As a result, the probability of an infectious case encountering a susceptible person drops dramatically.
For measles, the necessary threshold for herd immunity is 95 per cent. This means when 95 per cent of people in a population are immune, the remaining five per cent (including newborns, unvaccinated or undervaccinated children and immunodeficient people who cannot receive a measles vaccine) are also indirectly protected since the risk of measles virus transmission is significantly minimized.
By receiving two doses of a measles vaccine, one protects not only themselves but also the vulnerable members of their community. The only way to avoid measles and its serious complications, including proneness to a broad spectrum of unrelated infections, is to vaccinate widely, to engage those who are hesitant to have their children immunized in a respectful dialogue, and to educate the public regarding the unparalleled benefits of measles vaccines.
It is also crucial to isolate infected individuals for four days after the appearance of a measles rash to prevent measles virus transmission to others.
In Canada, measles has been a nationally notifiable disease since 1924 (except between 1959 and 1968), and the Canadian Measles and Rubella Surveillance System (CMRSS) ensures the weekly collection of measles data from every province and territory, including zero report submissions.
The Canadian government says it will donate up to 200,000 vaccine doses to fight the mpox outbreak in Congo and other African countries.
It says the donated doses of Imvamune will come from Canada’s existing supply and will not affect the country’s preparedness for mpox cases in this country.
Minister of Health Mark Holland says the donation “will help to protect those in the most affected regions of Africa and will help prevent further spread of the virus.”
Dr. Madhukar Pai, Canada research chair in epidemiology and global health, says although the donation is welcome, it is a very small portion of the estimated 10 million vaccine doses needed to control the outbreak.
Vaccine donations from wealthier countries have only recently started arriving in Africa, almost a month after the World Health Organization declared the mpox outbreak a public health emergency of international concern.
A few days after the declaration in August, Global Affairs Canada announced a contribution of $1 million for mpox surveillance, diagnostic tools, research and community awareness in Africa.
On Thursday, the Africa Centres for Disease Control and Prevention said mpox is still on the rise and that testing rates are “insufficient” across the continent.
Jason Kindrachuk, Canada research chair in emerging viruses at the University of Manitoba, said donating vaccines, in addition to supporting surveillance and diagnostic tests, is “massively important.”
But Kindrachuk, who has worked on the ground in Congo during the epidemic, also said that the international response to the mpox outbreak is “better late than never (but) better never late.”
“It would have been fantastic for us globally to not be in this position by having provided doses a much, much longer time prior than when we are,” he said, noting that the outbreak of clade I mpox in Congo started in early 2023.
Clade II mpox, endemic in regions of West Africa, came to the world’s attention even earlier — in 2022 — as that strain of virus spread to other countries, including Canada.
Two doses are recommended for mpox vaccination, so the donation may only benefit 100,000 people, Pai said.
Pai questioned whether Canada is contributing enough, as the federal government hasn’t said what percentage of its mpox vaccine stockpile it is donating.
“Small donations are simply not going to help end this crisis. We need to show greater solidarity and support,” he said in an email.
“That is the biggest lesson from the COVID-19 pandemic — our collective safety is tied with that of other nations.”
This report by The Canadian Press was first published Sept. 13, 2024.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.
The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.
Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.
“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”
The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.
A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.
Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.
“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.
Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.
The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.
“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.
This report by The Canadian Press was first published Sept. 11, 2024.
ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.
Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.
Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.
Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.
The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.
“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.
Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.
Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.
Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.
A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.
This report by The Canadian Press was first published Sept. 10, 2024.
