Cancer is a large group of diseases that can start in almost any organ or tissue of the body when abnormal cells grow uncontrollably, and go beyond their usual boundaries to invade adjoining parts of the body. According to the World Health Organization (WHO), it is the second most common cause of death globally, accounting for millions of deaths every year. Lung, prostate, colorectal, stomach and liver cancer are the most common types of cancer in men, while breast, colorectal, lung, cervical and thyroid cancer are the most common among women. However, these are not necessarily the deadliest forms of cancer.

What makes cancer the deadliest depends upon how many people have it and what percentage of those people actually survive. Cancer researchers determine this on the basis of five-year relative survival. This is the percentage of people who are expected to survive the effects of a given cancer, excluding their risk of other possible causes of death, for five years past a diagnosis. It is also important to note that what makes cancer really deadly is that practically no cure for it. A cure for cancer would imply that there are no cancerous cells remaining in the body.

Here are the 5 deadliest cancers in the U.S., according to SEER five-year relative survival data for cases diagnosed between 2014 and 2020.

1. Pancreatic cancer occurs when cells in your pancreas, a gland in your abdomen that aids digestion, mutate and multiply out of control, forming a tumour. Major risk factors include smoking, obesity, diabetes, chronic pancreatitis, certain genetic mutations and environmental chemical exposure.

2. Esophageal cancer develops in the oesophagus, which is the tube that connects your throat to your stomach.

3. Liver cancer and intrahepatic bile duct cancer originate in the liver or bile ducts, often linked to hepatitis infections, heavy alcohol use, obesity, and aflatoxin exposure.

4. Lung and bronchus cancer primarily caused by smoking, secondhand smoke, and environmental pollutants, affects the lungs and airways, making it the leading cause of cancer death in the US.

5. Acute myeloid leukaemia (AML) is an aggressive blood and bone marrow cancer that progresses rapidly, often linked to genetic mutations, radiation exposure, and certain chemicals.

ALSO READ: Why Are Lifestyle Factors Making Millennials Vulnerable To Cancer?

Sri Lanka is facing its worst dengue outbreak in over a decade, with 76,044 cases and 56 deaths reported so far in 2026, according to the National Dengue Control Unit (NDCU).

With the onset of the monsoon season, infections have surged sharply. While 8,590 cases were reported in May, the number more than doubled to 21,537 in June. In the first 19 days of July alone, 20,666 cases were recorded, including 2,895 new infections on July 21, the NDCU said.

The country has reported 56 dengue-related deaths this year, with a case fatality rate of 0.07%. According to the World Health Organization (WHO), global dengue cases have risen from around 500,000 in 2000 to 14.4 million in 2024.

Western Province Worst Hit

Sri Lanka's Western Province remains the hardest-hit region, accounting for more than half of all infections nationwide. Health officials have also identified 162 high-risk areas for dengue transmission, Asia News reported.

According to the NDCU, the Ministry of Health is currently conducting surveillance programmes across 63 high-risk divisions. The country is also deploying military drones to identify stagnant water on rooftops and other mosquito breeding sites.

Public Health System Under Pressure

According to Reuters, Sri Lanka's public health services and hospitals are battling the country's worst dengue outbreak in nearly a decade, with the armed forces assisting efforts to contain the spread.

The response includes air force drones tracking rooftop pools of stagnant water after monsoon rains, while military and police personnel are helping inspect homes, construction sites and schools to eliminate mosquito breeding grounds.

Public health workers were "stretched to their limit," said Kapila Kannangara, Acting Director General of the National Dengue Control Unit.

"The number of patients is high, and the severity of the cases is high," he said, adding that about 75% of cases are linked to the more virulent DENV-2 strain, which is spreading rapidly.

Health officials expect infections to decline as monsoon rains weaken in August but warn that cases could rise again from November with the arrival of the island's second annual monsoon season.

What Is Dengue?

Dengue is a viral infection transmitted primarily by Aedes mosquitoes and is common in tropical and subtropical regions worldwide.

Most infections cause high fever and flu-like illness. However, some cases can progress to severe dengue (dengue hemorrhagic fever), which may lead to severe bleeding, shock and death.

Dengue is the most widespread viral disease transmitted by Aedes mosquitoes. More than 3.9 billion people across over 132 countries are at risk, with an estimated 96 million symptomatic cases and around 40,000 deaths reported each year globally.

Symptoms of Dengue Fever

Symptoms usually appear 4–10 days after the bite of an infected mosquito and may include:

• High fever
• Severe headache
• Pain behind the eyes
• Joint and muscle pain
• Nausea and vomiting
• Fatigue
• Skin rash appearing a few days after fever begins

In severe cases, dengue can cause excessive bleeding, a sudden drop in blood pressure and organ complications.

How to Prevent Dengue

Preventing dengue focuses on avoiding mosquito bites and eliminating breeding sites. Measures include:

• Using insect repellents containing DEET
• Wearing long-sleeved clothing, especially during dawn and dusk
• Installing screens on windows and doors
• Sleeping under mosquito nets in endemic areas
• Removing stagnant water from flower pots, gutters and containers
• Using mosquito traps or insecticide-treated materials in mosquito-prone areas

The US Centers for Disease Control and Prevention (CDC) and the UK Health Security Agency (UKHSA) have issued travel health advisories warning travelers about the growing risks of mosquito-borne diseases, including chikungunya and yellow fever.

The CDC has issued a Level 2 Travel Health Notice for Costa Rica following a chikungunya outbreak, while UK health authorities have alerted travelers about rising imported chikungunya cases and yellow fever activity across multiple countries.

CDC Issues Level 2 Travel Health Notice

The CDC warned American travelers to "practice enhanced precautions" after Costa Rica reported a chikungunya outbreak.

On July 1, Costa Rica's Ministry of Health declared an active outbreak in the oceanside community of Playa Langosta in the western province of Guanacaste..

An epidemiological survey identified 45 suspected cases, of which four were laboratory confirmed, while 17 others were considered likely linked to the outbreak.

According to the US Embassy in Costa Rica, the cases include both Costa Rican nationals and foreign visitors. The embassy said local transmission means the virus is now circulating among the local mosquito population rather than being limited to infected travelers.

Costa Rica has reported 16 total cases this year, with the previous reported case dating back to 2017.

UKHSA Warns Over Rising Chikungunya Cases

The UK Health Security Agency issued a warning for holidaymakers travelling to affected regions as imported chikungunya cases continue to rise.

"Are you, or someone you know, heading off on a tropical trip? It's worth being aware of chikungunya, a mosquito-borne virus that can cause severe joint pain. Check out our blog post to learn how to stay protected," the UKHSA said in a post on X.

UKHSA reported 112 confirmed and probable chikungunya cases among travelers returning to England, Wales and Northern Ireland in 2024—almost one and a half times the number reported in 2023.

"Travel to India accounted for the majority of these cases, followed by travel to Pakistan and Brazil – all popular destinations for people travelling from the UK," the agency added.

Yellow Fever Alert Issued for Multiple Countries

The UK government-backed Travel Health Pro has also warned travelers about increasing yellow fever activity.

Since the beginning of 2026, 95 confirmed yellow fever cases have been reported globally.

Confirmed cases have been reported in:

• Bolivia
• Brazil
• Colombia
• Ecuador
• Peru
• Venezuela
• Burkina Faso
• Central African Republic
• Cameroon

What Is Chikungunya?

Chikungunya is a mosquito-borne viral disease transmitted primarily by Aedes aegypti and Aedes albopictus mosquitoes, the same mosquitoes that spread dengue fever.

Symptoms usually appear three to seven days after an infected mosquito bite and include:

• Sudden fever
• Severe joint pain
• Headache
• Nausea
• Fatigue
• Rash (in about half of cases)

Unlike dengue, chikungunya can leave lingering effects, with joint pain and fatigue lasting for weeks, months or even years.

People at higher risk of severe illness include:

• Newborns
• Older adults
• People with hypertension
• People with diabetes
• People with heart disease

The mosquitoes responsible for spreading chikungunya commonly breed in stagnant water found in overhead tanks, coolers and unused containers.

What Is Yellow Fever?

Yellow fever is a viral disease transmitted through the bite of infected mosquitoes. The infection can be severe and may become fatal in some cases if not managed appropriately. Vaccination is recommended before travelling to certain affected regions.

Initial Symptoms

• Fever
• Chills
• Severe headache
• Back pain
• General body aches
• Nausea
• Vomiting
• Fatigue
• Weakness

Severe Symptoms

• High fever
• Yellowing of the skin or eyes (jaundice)
• Bleeding
• Shock
• Organ failure

The US Food and Drug Administration (FDA) has identified a new Cyclospora outbreak, which is not related to ongoing outbreaks in the country causing watery diarrhea and hospitalizations among thousands.

The agency said the outbreak has sickened 72 people and is linked to an unspecified product. The FDA said the source has "not yet been identified."

The announcement comes as the US continues to report one of its largest cyclospora outbreaks. According to the US Centers for Disease Control and Prevention (CDC), there have been 4,173 laboratory-confirmed and domestically acquired cases of cyclosporiasis across 41 states since May 1.

A total of 308 people with confirmed infections have been hospitalized, but no deaths have been reported.

The CDC also reported 767 travel-associated cases during the same period, resulting in 33 hospitalizations and no deaths. These cases were linked to contaminated food or water consumed outside the US.

Lettuce-Linked Outbreak In 5 states

According to the Michigan Department of Health and Human Services, a Cyclospora outbreak linked to iceberg lettuce distributed by Taylor Farms has sickened 7,664 people across Indiana, Kentucky, Michigan, Ohio and West Virginia, with 160 hospitalizations.

Michigan has reported about 7,000 cases, while Ohio has recorded nearly 3,500 cases, according to the Toledo-Lucas County Health Department.

“I want to stress that our investigation continues, including into other potential sources and commodities for other clusters of illness,” said Kyle Diamantas, acting FDA commissioner. Meanwhile, Health and Human Services Secretary Robert F. Kennedy Jr. this week said the outbreak is “under control.”

Why Is It So Difficult To Find the Source?

Also read: Cyclospora Parasite Outbreak: Why You Should Avoid Packaged Salads and Go For Loose Greens

According to experts, Cyclospora infection caused by the parasite Cyclospora cayetanensis is much harder to trace than common foodborne bacteria such as E. coli and Salmonella.

Investigators typically use DNA fingerprinting to connect bacterial infections to contaminated food through laboratory networks such as PulseNet. However, this method is much less effective for Cyclospora because the parasite has a more complex genetic makeup, making it difficult to link infections to a single food item or supplier.

Dr. Max Teplitski, former head of the Division of Food Safety at the US Department of Agriculture and now chief science officer at the International Fresh Produce Association, said the parasite remains one of the most difficult foodborne pathogens to investigate, contributing to delays in identifying the outbreak source, CNN reported.

How To Prevent Cyclospora Infection

Read More: Cyclospora Parasite Spreads to More US States: Foods to Avoid Right Now

The CDC recommends the following steps to reduce the risk of infection:

• Wash your hands thoroughly with soap and water before and after handling fresh produce.
• Rinse fruits and vegetables under running water before eating, cutting or cooking them.
• Do not rewash produce labeled "prewashed."
• Scrub firm produce, such as melons and cucumbers, with a clean produce brush.
• Cut away bruised or damaged portions before eating.
• Refrigerate cut, peeled or cooked fruits and vegetables within two hours.

Cyclospora spreads through food or water contaminated with human feces and is not transmitted directly from person to person.

Dr. Darien Sutton, an emergency medicine physician and ABC News medical correspondent, emphasized that alcohol-based hand sanitizers are ineffective against the parasite. "This type of parasite doesn't easily go away with alcohol-based hand sanitizer. So, good old handwashing is really key here," Sutton said.