Causes of Measles
Causes of measles are rooted in a highly contagious viral infection caused by the measles virus. This virus belongs to the Paramyxoviridae family and the Morbillivirus genus. Measles spreads quickly, often causing outbreaks in communities with low vaccination coverage. Understanding the causes of measles helps explain why the disease spreads and why prevention is so important.
The Measles Virus and Its Mechanism
The measles virus infects the respiratory tract and spreads through the body. It enters the body through inhaled droplets or contact with nasal or throat secretions. Once inside, it multiplies in the respiratory tract and lymph nodes. Then, it moves into the bloodstream, affecting multiple organs and causing classic measles symptoms.
The virus also weakens the immune system, leaving people more prone to secondary infections like pneumonia or ear infections. Measles is extremely contagious. If one person has the virus, up to 90% of nearby unvaccinated people can also become infected. This is why herd immunity through vaccination is crucial.
Human-to-Human Transmission
The virus spreads almost entirely from person to person. It travels through airborne droplets when an infected person coughs, sneezes, or talks. Droplets can stay in the air or land on surfaces where the virus survives up to two hours. Anyone who breathes in the droplets or touches contaminated surfaces and then touches their mouth or nose can catch measles.
People are contagious from about four days before the rash appears to four days after. This means they can spread the virus without knowing they are sick, which makes early detection and isolation important.
Unvaccinated Populations
A major cause of measles outbreaks is low immunisation. The measles vaccine has greatly reduced cases worldwide, but many areas still have low coverage. Factors include misinformation, vaccine hesitancy, poor healthcare access, and political problems.
In developed countries, some people refuse vaccination due to mistrust or anti-vaccine beliefs. In low-income regions, issues like vaccine storage, funding shortages, and lack of clinics hinder immunisation. These gaps allow measles to spread, especially among children under five and adults with weak immunity.
Compromised Immune Systems
Weakened immunity also increases the risk of measles. People with HIV/AIDS, cancer patients on chemotherapy, or organ transplant recipients are more vulnerable. Their bodies cannot fight the virus effectively, making infection more likely and severe.
Pregnant individuals face higher risks. Measles during pregnancy can cause miscarriage, premature birth, or low birth weight.
International Travel and Globalisation
Travel plays a role in measles spread. People from countries with outbreaks can carry the virus to areas where local transmission is low. Airports, planes, and tourist spots become hubs for infection.
These “imported cases” can start new outbreaks in communities with low vaccination rates. This is why measles can flare up even in countries that once eliminated it.
Malnutrition and Vitamin A Deficiency
Poor nutrition, especially low vitamin A, increases the risk and severity of measles. Vitamin A supports immune function and protects mucosal surfaces. Children lacking vitamin A often have longer, more severe illness, with higher risk of complications like blindness or death.
General malnutrition weakens the immune system, making it harder to fight infections. This is particularly dangerous where food insecurity overlaps with low vaccination coverage.
Waning Immunity or Vaccine Failure
Some vaccinated individuals may still get measles. This can occur due to vaccine failure or waning immunity. Primary failure happens when the vaccine never triggers immunity, while secondary failure occurs when protection fades over time.
The measles vaccine is very effective—about 93% after one dose and 97% after two doses—but no vaccine is perfect. People with weak immunity may still fail to respond fully, even with complete vaccination.
Social Determinants and Environmental Factors
Other causes of measles include poor sanitation, overcrowding, lack of healthcare, and low health knowledge. Dense urban areas, refugee camps, and remote communities allow faster spread.
Conflict, displacement, and political instability also disrupt vaccination programs. For example, during the COVID-19 pandemic, many immunisation campaigns were paused, allowing measles to resurface.
