What combos are available and what are their effects?

Solution 1:

From the Plague Inc. Wiki:

Standard combos

Oops symptom combo

Diarrhoea + Sneezing

Sneezing and diarrhoea are causing unwanted accidents, lowering productivity and drawing attention to [disease name]

• Slightly increases Infectivity
• Slightly increases Severity
• Slightly slows down Cure Research

Profuse bleeding symptom combo

Haemophilia + Skin Lesions

Haemophilia and skin lesions are causing the infected to have blood pouring out of their skin, making [disease name] far more dangerous

• Slightly increases Lethality
• Large increase in Infectivity
• Even larger increase in Infectivity when paired with Blood 1 and 2 transmissions

Projectile Vomiting

Coughing + Vomiting

Coughing and vomiting are causing the infected to projectile vomit, increasing the infectivity of [disease name]

• Slightly increases Infectivity

Swine Flu symptom combo

Coughing + Diarrhoea + Insomnia + Pneunomia + Vomiting + Livestock 2

[Disease name] has similar symptoms to Swine Flu. Doctors researching the cure are wasting time looking into cures for Swine Flu. Cure will take longer

• Slightly slows down Cure Research

Public Defecation symptom combo

Diarrhoea + Insanity

Diarrhoea and insanity are causing the people to defecate in public (and everywhere else!) Everyone is increasingly focused on developing a cure

• Slightly increases Infectivity
• Slightly speeds up Cure Research

Waking Dead symptom combo

Anaemia + Insomnia

Insomnia and anaemia are causing people to walk around grey with tiredness. Scientists working on the cure for [disease name] are less productive

• Slightly slows down Cure Research

Necroa Virus Combos

Vampire Bat

Vampiric Hunger + Bat 2

• Slightly increases Severity
• Slightly increases Infectivity
• Slightly increases Lethality

Tank

Anabolic Boost + Bone Dysplasia

• Slightly increases Severity

Spitter

Naja Mortis + Enhanced Sensory Integration

• Slightly increases Severity

Boomer

Autothysis + Liquefactive Necrosis

• Slightly increases Severity

Cranial Dispersion

Cranial Elephantitis + Air 3

• Increases Severity

Walking Contradiction

Photophobia + Cathameral Shift

• Slightly decreases Severity

Runner

Enhanced Motor Control + Engorged Quadriceps

• Slightly increases Severity

Bath Time

Autophagia + Polyphagia + Cannibalism

• Increases Infectivity

The Neurax Worm does not feature any Combos.